blocks|key|871146|text|你也可以在Javascript中覆盖toString。请参见示例：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|871147|​|871148|function+Foo()+{}

//+toString+override+added+to+prototype+of+Foo+class
Foo.prototype.toString+=+function()+{
++return+"[object+Foo]";
}

var+f+=+new+Foo();
console.log(""+%2B+f);+//+console+displays+[object+Foo]|code-block|syntax|javascript|871149|871150|有关如何在JavaScript中确定对象类型名称的信息，请参阅this讨论。|871151|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/332422/how-do-i-get-the-name-of-an-objects-type-in-javascript^0|I|8|0|0|0|0|V|4|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|11|8|@]|D|@]|E|$K|L]]|$1|M|3|G|5|6|7|12|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|P|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|Q|$R|$5|S|T|U|E|$V|W]]]]

<p>You can override <code>toString</code> in Javascript as well. See example:</p>
<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>function Foo() {}

// toString override added to prototype of Foo class
Foo.prototype.toString = function() {
  return "[object Foo]";
}

var f = new Foo();
console.log("" + f); // console displays [object Foo]</code></pre>
</div>
</div>
</p>
<p>See <a href="https://stackoverflow.com/questions/332422/how-do-i-get-the-name-of-an-objects-type-in-javascript">this</a> discussion on how to determine object type name in JavaScript.</p>


blocks|key|871186|text|Chrome控制台日志允许您检查对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|871187|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

<p>The Chrome console log allows you to inspect the object.</p>


blocks|key|871264|text|只需覆盖toString()方法即可。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|871265|简单的例子：|871266|var+x+=+{foo:+1,+bar:+true,+baz:+'quux'};
x.toString();+//+returns+"[object+Object]"
x.toString+=+function+()+{
++++var+s+=+[];
++++for+(var+k+in+this)+{
++++++++if+(this.hasOwnProperty(k))+s.push(k+%2B+':'+%2B+this[k]);
++++}
++++return+'{'+%2B+s.join()+%2B+'}';
};
x.toString();+//+returns+something+more+useful|code-block|syntax|javascript|871267|当你定义一个新的类型时，它会做得更好：|871268|function+X()
{
++++this.foo+=+1;
++++this.bar+=+true;
++++this.baz+=+'quux';
}

X.prototype.toString+=+/*+same+function+as+before+*/

new+X().toString();+//+returns+"{foo:1,bar:true,baz:quux}"|871269|entityMap^0|4|A|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|X|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|R|$]]

<p>Just override the <code>toString()</code> method.</p>

<p>Simple example:</p>

<pre><code>var x = {foo: 1, bar: true, baz: 'quux'};
x.toString(); // returns "[object Object]"
x.toString = function () {
    var s = [];
    for (var k in this) {
        if (this.hasOwnProperty(k)) s.push(k + ':' + this[k]);
    }
    return '{' + s.join() + '}';
};
x.toString(); // returns something more useful
</code></pre>

<p>It does even better when you define a new type:</p>

<pre><code>function X()
{
    this.foo = 1;
    this.bar = true;
    this.baz = 'quux';
}

X.prototype.toString = /* same function as before */

new X().toString(); // returns "{foo:1,bar:true,baz:quux}"
</code></pre>


blocks|key|871325|text|您可以为任何自定义对象提供它们自己的toString方法，或者编写一个通用的方法，以便在您正在查看的对象上进行调用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|871326|Function.prototype.named=+function(ns){
++++var+Rx=++/function\s%2B([%5E(\s]%2B)\s*\(/,+tem=+this.toString().match(Rx)+%7C%7C+"";
++++if(tem)+return+tem[1];
++++return+'unnamed+constructor'
}

function+whatsit(what){
++++if(what===undefined)return+'undefined';
++++if(what===+null)+return+'null+object';
++++if(what==+window)+return+'Window+object';
++++if(what.nodeName){
++++++++return+'html+'%2Bwhat.nodeName;
++++}
++++try{
++++++++if(typeof+what==+'object'){
++++++++++++return+what.constructor.named();
++++++++}
++++}
++++catch(er){
++++++++return+'Error+reading+Object+constructor';
++++}
++++var+w=typeof+what;
++++return+w.charAt(0).toUpperCase()%2Bw.substring(1);
}|code-block|syntax|javascript|871327|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>You can give any custom objects their own toString methods, or write a general one that you can call on the object you are looking at-</p>

<pre><code>Function.prototype.named= function(ns){
    var Rx=  /function\s+([^(\s]+)\s*\(/, tem= this.toString().match(Rx) || "";
    if(tem) return tem[1];
    return 'unnamed constructor'
}

function whatsit(what){
    if(what===undefined)return 'undefined';
    if(what=== null) return 'null object';
    if(what== window) return 'Window object';
    if(what.nodeName){
        return 'html '+what.nodeName;
    }
    try{
        if(typeof what== 'object'){
            return what.constructor.named();
        }
    }
    catch(er){
        return 'Error reading Object constructor';
    }
    var w=typeof what;
    return w.charAt(0).toUpperCase()+w.substring(1);
}
</code></pre>


blocks|key|654097|text|如果包含Prototype+JavaScript+Library，则可以使用Object.inspect()来获得更有用的表示，而不是覆盖toString()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|654098|大多数流行的框架都包含类似的东西。|654099|entityMap|0|LINK|mutability|MUTABLE|url|http://www.prototypejs.org/^0|12|G|1X|A|4|S|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

<p>Rather than overriding <code>toString()</code>, if you include the <a href="http://www.prototypejs.org/" rel="nofollow">Prototype JavaScript Library</a>, you can use <code>Object.inspect()</code> to get a much more useful representation.</p>

<p>Most popular frameworks include something similar.</p>


blocks|key|654161|text|在浏览器JS中获得可调试输出的一种简单方法是将对象序列化为JSON。这样你就可以像这样打电话|type|unstyled|depth|inlineStyleRanges|entityRanges|data|654162|console.log+("Blah:+"+%2B+JSON.stringify(object));|code-block|syntax|javascript|654163|举个例子，alert("Blah!+"+%2B+JSON.stringify({key:+"value"}));生成一个文本为Blah!+{"key":"value"}的警报|offset|length|style|CODE|654164|entityMap^0|0|0|5|1D|1P|L|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

<p>An easy way to get debuggable output in browser JS is to just serialize the object to JSON. So you could make a call like</p>

<pre><code>console.log ("Blah: " + JSON.stringify(object));
</code></pre>

<p>So for an example, <code>alert("Blah! " + JSON.stringify({key: "value"}));</code> produces an alert with the text <code>Blah! {"key":"value"}</code></p>


blocks|key|654211|text|如果对象是您自己定义的，则始终可以添加toString替代。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|654212|​|654213|//Defined+car+Object
var+car+=+{
++type:+"Fiat",
++model:+500,
++color:+"white",
++//.toString()+Override
++toString:+function()+{
++++return+this.type;
++}
};

//Various+ways+to+test+.toString()+Override
console.log(car.toString());
console.log(car);
alert(car.toString());
alert(car);

//Defined+carPlus+Object
var+carPlus+=+{
++type:+"Fiat",
++model:+500,
++color:+"white",
++//.toString()+Override
++toString:+function()+{
++++return+'type:+'+%2B+this.type+%2B+',+model:+'+%2B+this.model+%2B+',+color:++'+%2B+this.color;
++}
};

//Various+ways+to+test+.toString()+Override
console.log(carPlus.toString());
console.log(carPlus);
alert(carPlus.toString());
alert(carPlus);|code-block|syntax|javascript|654214|654215|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|N|8|@]|9|@]|A|$G|H]]|$1|I|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|K|$]]

<p>If the object is defined by yourself you can always add a toString override.</p>

<p><div class="snippet" data-lang="js" data-hide="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>//Defined car Object
var car = {
  type: "Fiat",
  model: 500,
  color: "white",
  //.toString() Override
  toString: function() {
    return this.type;
  }
};

//Various ways to test .toString() Override
console.log(car.toString());
console.log(car);
alert(car.toString());
alert(car);

//Defined carPlus Object
var carPlus = {
  type: "Fiat",
  model: 500,
  color: "white",
  //.toString() Override
  toString: function() {
    return 'type: ' + this.type + ', model: ' + this.model + ', color:  ' + this.color;
  }
};

//Various ways to test .toString() Override
console.log(carPlus.toString());
console.log(carPlus);
alert(carPlus.toString());
alert(carPlus);</code></pre>
</div>
</div>
    </p>


blocks|key|871575|text|首先覆盖对象或原型的toString：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|871576|var+Foo+=+function(){};
Foo.prototype.toString+=+function(){return+'Pity+the+Foo';};

var+foo+=+new+Foo();|code-block|syntax|javascript|871577|然后转换为字符串以查看对象的字符串表示：|871578|//using+JS+implicit+type+conversion
console.log(''+%2B+foo);|871579|如果您不喜欢额外的输入，您可以创建一个函数，将其参数的字符串表示形式记录到控制台：|871580|var+puts+=+function(){
++++var+strings+=+Array.prototype.map.call(arguments,+function(obj){
++++++++return+''+%2B+obj;
++++});
++++console.log.apply(console,+strings);
};|871581|用法：|871582|puts(foo)++//logs+'Pity+the+Foo'

puts(foo,+[1,2,3],+{a:+2})+//logs+'Pity+the+Foo+1,2,3+[object+Object]'|871583|更新|871584|E2015为这些东西提供了更好的语法，但是您必须使用像Babel这样的转译器|871585|//+override+`toString`
class+Foo+{
++toString(){
++++return+'Pity+the+Foo';
++}
}

const+foo+=+new+Foo();

//+utility+function+for+printing+objects+using+their+`toString`+methods
const+puts+=+(...any)+=>+console.log(...any.map(String));

puts(foo);+//+logs+'Pity+the+Foo'|871586|entityMap|0|LINK|mutability|MUTABLE|url|http://babeljs.io/^0|A|8|0|0|0|0|0|0|0|0|0|R|5|0|0|0^^$0|@$1|2|3|4|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1D|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1E|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1F|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1G|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1H|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1I|8|@]|D|@]|E|$]]|$1|U|3|V|5|H|7|1J|8|@]|D|@]|E|$I|J]]|$1|W|3|X|5|6|7|1K|8|@]|D|@]|E|$]]|$1|Y|3|Z|5|6|7|1L|8|@]|D|@$9|1M|A|1N|1|1O]]|E|$]]|$1|10|3|11|5|H|7|1P|8|@]|D|@]|E|$I|J]]|$1|12|3|-4|5|6|7|1Q|8|@]|D|@]|E|$]]]|13|$14|$5|15|16|17|E|$18|19]]]]

<p>First override <code>toString</code> for your object or the prototype:</p>

<pre><code>var Foo = function(){};
Foo.prototype.toString = function(){return 'Pity the Foo';};

var foo = new Foo();
</code></pre>

<p>Then convert to string to see the string representation of the object:</p>

<pre><code>//using JS implicit type conversion
console.log('' + foo);
</code></pre>

<p>If you don't like the extra typing, you can create a function that logs string representations of its arguments to the console:</p>

<pre><code>var puts = function(){
    var strings = Array.prototype.map.call(arguments, function(obj){
        return '' + obj;
    });
    console.log.apply(console, strings);
};
</code></pre>

<p>Usage:</p>

<pre><code>puts(foo)  //logs 'Pity the Foo'

puts(foo, [1,2,3], {a: 2}) //logs 'Pity the Foo 1,2,3 [object Object]'
</code></pre>

<h2>Update</h2>

<p>E2015 provides much nicer syntax for this stuff, but you'll have to use a transpiler like <a href="http://babeljs.io">Babel</a>:</p>

<pre><code>// override `toString`
class Foo {
  toString(){
    return 'Pity the Foo';
  }
}

const foo = new Foo();

// utility function for printing objects using their `toString` methods
const puts = (...any) =&gt; console.log(...any.map(String));

puts(foo); // logs 'Pity the Foo'
</code></pre>


blocks|key|871636|text|A+simple+format+Date+function+using+Javascript+prototype,+it+can+be+used+for+your+purpose

https://gist.github.com/cstipkovic/3983879+:

Date.prototype.formatDate+=+function+(format)+{
++++var+date+=+this,
++++++++day+=+date.getDate(),
++++++++month+=+date.getMonth()+%2B+1,
++++++++year+=+date.getFullYear(),
++++++++hours+=+date.getHours(),
++++++++minutes+=+date.getMinutes(),
++++++++seconds+=+date.getSeconds();

++++if+(!format)+{
++++++++format+=+"MM/dd/yyyy";
++++}

++++format+=+format.replace("MM",+month.toString().replace(/%5E(\d)$/,+'0$1'));

++++if+(format.indexOf("yyyy")+>+-1)+{
++++++++format+=+format.replace("yyyy",+year.toString());
++++}+else+if+(format.indexOf("yy")+>+-1)+{
++++++++format+=+format.replace("yy",+year.toString().substr(2,+2));
++++}

++++format+=+format.replace("dd",+day.toString().replace(/%5E(\d)$/,+'0$1'));

++++if+(format.indexOf("t")+>+-1)+{
++++++++if+(hours+>+11)+{
++++++++++++format+=+format.replace("t",+"pm");
++++++++}+else+{
++++++++++++format+=+format.replace("t",+"am");
++++++++}
++++}

++++if+(format.indexOf("HH")+>+-1)+{
++++++++format+=+format.replace("HH",+hours.toString().replace(/%5E(\d)$/,+'0$1'));
++++}

++++if+(format.indexOf("hh")+>+-1)+{
++++++++if+(hours+>+12)+{
++++++++++++hours+-=+12;
++++++++}

++++++++if+(hours+===+0)+{
++++++++++++hours+=+12;
++++++++}
++++++++format+=+format.replace("hh",+hours.toString().replace(/%5E(\d)$/,+'0$1'));
++++}

++++if+(format.indexOf("mm")+>+-1)+{
++++++++format+=+format.replace("mm",+minutes.toString().replace(/%5E(\d)$/,+'0$1'));
++++}

++++if+(format.indexOf("ss")+>+-1)+{
++++++++format+=+format.replace("ss",+seconds.toString().replace(/%5E(\d)$/,+'0$1'));
++++}

++++return+format;
};|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|871637|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>A simple format Date function using Javascript prototype, it can be used for your purpose

https://gist.github.com/cstipkovic/3983879 :

Date.prototype.formatDate = function (format) {
    var date = this,
        day = date.getDate(),
        month = date.getMonth() + 1,
        year = date.getFullYear(),
        hours = date.getHours(),
        minutes = date.getMinutes(),
        seconds = date.getSeconds();

    if (!format) {
        format = "MM/dd/yyyy";
    }

    format = format.replace("MM", month.toString().replace(/^(\d)$/, '0$1'));

    if (format.indexOf("yyyy") &gt; -1) {
        format = format.replace("yyyy", year.toString());
    } else if (format.indexOf("yy") &gt; -1) {
        format = format.replace("yy", year.toString().substr(2, 2));
    }

    format = format.replace("dd", day.toString().replace(/^(\d)$/, '0$1'));

    if (format.indexOf("t") &gt; -1) {
        if (hours &gt; 11) {
            format = format.replace("t", "pm");
        } else {
            format = format.replace("t", "am");
        }
    }

    if (format.indexOf("HH") &gt; -1) {
        format = format.replace("HH", hours.toString().replace(/^(\d)$/, '0$1'));
    }

    if (format.indexOf("hh") &gt; -1) {
        if (hours &gt; 12) {
            hours -= 12;
        }

        if (hours === 0) {
            hours = 12;
        }
        format = format.replace("hh", hours.toString().replace(/^(\d)$/, '0$1'));
    }

    if (format.indexOf("mm") &gt; -1) {
        format = format.replace("mm", minutes.toString().replace(/^(\d)$/, '0$1'));
    }

    if (format.indexOf("ss") &gt; -1) {
        format = format.replace("ss", seconds.toString().replace(/^(\d)$/, '0$1'));
    }

    return format;
};
</code></pre>


blocks|key|871650|text|使用template+literals|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|871651|class+Foo+{
++toString()+{
+++++return+'I+am+foo';
++}
}

const+foo+=+new+Foo();
console.log(`${foo}`);+//+'I+am+foo'|code-block|syntax|javascript|871652|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals^0|2|H|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

<p>With <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals" rel="noreferrer">template literals</a>:</p>

<pre><code>class Foo {
  toString() {
     return 'I am foo';
  }
}

const foo = new Foo();
console.log(`${foo}`); // 'I am foo'
</code></pre>


blocks|key|871684|text|您可以在JS中扩展或覆盖|type|unstyled|depth|inlineStyleRanges|entityRanges|data|871685|​|871686|String.prototype.toString+=+function()+{
++++return+this+%2B+"..."
}
document.write("Sergio".toString());|code-block|syntax|javascript|871687|871688|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|N|8|@]|9|@]|A|$G|H]]|$1|I|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|K|$]]

<p>You can extend or override in JS</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>String.prototype.toString = function() {
    return this + "..."
}
document.write("Sergio".toString());</code></pre>
</div>
</div>
</p>


blocks|key|654411|text|下面是一个如何给Map对象加上字符串的例子：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|654412|++Map.prototype.toString+=+function()+{

++++let+result+=+{};

++++this.forEach((key,+value)+=>+{+result[key]+=+value;});

++++return+JSON.stringify(result);
++};|code-block|syntax|javascript|654413|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>Here's an example how to stringify a Map object:</p>

<pre><code>  Map.prototype.toString = function() {

    let result = {};

    this.forEach((key, value) =&gt; { result[key] = value;});

    return JSON.stringify(result);
  };
</code></pre>


blocks|key|654476|text|将'Symbol.toStringTag'属性添加到自定义对象或类。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|654477|分配给它的字符串值将是它的默认字符串描述，因为它是由Object.prototype.toString()方法在内部访问的。|style|CODE|654478|例如：|654479|class+Person+{
++constructor(name)+{
++++this.name+=+name
++}
++get+[Symbol.toStringTag]()+{
++++return+'Person';
++}
}

let+p+=+new+Person('Dan');
Object.prototype.toString.call(p);+//+[object+Person]|code-block|syntax|javascript|654480|​|654481|class+Person+{
++constructor(name)+{
++++this.name+=+name
++}
++get[Symbol.toStringTag]()+{
++++return+'Person';
++}
}

let+p+=+new+Person('Dan');
console.log(Object.prototype.toString.call(p));|654482|654483|某些Javascript类型(如地图和承诺)定义了内置toStringTag符号|654484|Object.prototype.toString.call(new+Map());+++++++//+"[object+Map]"
Object.prototype.toString.call(Promise.resolve());+//+"[object+Promise]"|654485|因为Symbol.toStringTag是一个well-known+symbol，所以我们可以引用它并验证上面的类型是否具有Symbol.toStringTag属性-|654486|new+Map()[Symbol.toStringTag]+//+'Map'
Promise.resolve()[Symbol.toStringTag]+//+'Promise'|654487|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toStringTag|1|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol#Well-known_symbols^0|1|K|0|0|Q|R|0|0|0|0|0|0|R|B|0|0|2|I|N|H|1|0|0^^$0|@$1|2|3|4|5|6|7|1B|8|@]|9|@$A|1C|B|1D|1|1E]]|C|$]]|$1|D|3|E|5|6|7|1F|8|@$A|1G|B|1H|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|1I|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|1J|8|@]|9|@]|C|$M|N]]|$1|O|3|P|5|6|7|1K|8|@]|9|@]|C|$]]|$1|Q|3|R|5|L|7|1L|8|@]|9|@]|C|$M|N]]|$1|S|3|P|5|6|7|1M|8|@]|9|@]|C|$]]|$1|T|3|U|5|6|7|1N|8|@$A|1O|B|1P|F|G]]|9|@]|C|$]]|$1|V|3|W|5|L|7|1Q|8|@]|9|@]|C|$M|N]]|$1|X|3|Y|5|6|7|1R|8|@$A|1S|B|1T|F|G]]|9|@$A|1U|B|1V|1|1W]]|C|$]]|$1|Z|3|10|5|L|7|1X|8|@]|9|@]|C|$M|N]]|$1|11|3|-4|5|6|7|1Y|8|@]|9|@]|C|$]]]|12|$13|$5|14|15|16|C|$17|18]]|19|$5|14|15|16|C|$17|1A]]]]

<p>Add the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toStringTag" rel="noreferrer">'Symbol.toStringTag'</a> property to the custom object or class.</p>

<p>The string value which is assigned to it will be its default string description because it is accessed internally by the <code>Object.prototype.toString()</code> method. </p>

<p>For example:</p>

<pre><code>class Person {
  constructor(name) {
    this.name = name
  }
  get [Symbol.toStringTag]() {
    return 'Person';
  }
}

let p = new Person('Dan');
Object.prototype.toString.call(p); // [object Person]
</code></pre>

<p><div class="snippet" data-lang="js" data-hide="true" data-console="true" data-babel="false">
<div class="snippet-code snippet-currently-hidden">
<pre class="snippet-code-js lang-js prettyprint-override"><code>class Person {
  constructor(name) {
    this.name = name
  }
  get[Symbol.toStringTag]() {
    return 'Person';
  }
}

let p = new Person('Dan');
console.log(Object.prototype.toString.call(p));</code></pre>
</div>
</div>
</p>

<p>Some Javascript types such as Maps and Promises have a built-in <code>toStringTag</code> symbol defined </p>

<pre><code>Object.prototype.toString.call(new Map());       // "[object Map]"
Object.prototype.toString.call(Promise.resolve()); // "[object Promise]"
</code></pre>

<p>Because <code>Symbol.toStringTag</code> is a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol#Well-known_symbols" rel="noreferrer">well-known symbol</a>, we can reference it and verify that the above types do have the Symbol.toStringTag property -</p>

<pre><code>new Map()[Symbol.toStringTag] // 'Map'
Promise.resolve()[Symbol.toStringTag] // 'Promise'
</code></pre>


<p>When I <code>console.log()</code> an object in my JavaScript program, I just see the output <code>[object Object]</code>, which is not very helpful in figuring out what object (or even what type of object) it is.</p>

<p>In C# I'm used to overriding <code>ToString()</code> to be able to customize the debugger representation of an object. Is there anything similar I can do in JavaScript?</p>


Is it possible to override JavaScript's toString() function to provide meaningful output for debugging?

调试器

JSON

当我在JavaScript程序中console.log()一个对象时，我只看到输出的[object Object]，这对确定它是什么对象(甚至是什么类型的对象)没有多大帮助。在C#中，我习惯于重写ToString()，以便能够定制对象的调试器表示。我在JavaScript中也可以做类似的事情吗？

问有没有可能覆盖JavaScript的toString()函数来为调试提供有意义的输出？
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问有没有可能覆盖JavaScript的toString()函数来为调试提供有意义的输出？
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