blocks|key|883846|text|var+
print_names+=+function()+{
++++console.log.apply(+this,+arguments+);
};

print_names(+1,+2,+3,+4+);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|883847|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>var 
print_names = function() {
 console.log.apply( this, arguments );
};

print_names( 1, 2, 3, 4 );
</code></pre>

blocks|key|883717|text|function+print_args()+{
++++for(var+i=0;+i<arguments.length;+i%2B%2B)
++++++++console.log(arguments[i])
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|883718|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>function print_args() {
 for(var i=0; i&lt;arguments.length; i++)
 console.log(arguments[i])
}
</code></pre>

blocks|key|1098605|text|有一个名为arguments的隐藏对象传递给JavaScript中的每个函数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1098606|您只需使用arguments.length来获取传递给函数的参数数量。|1098607|要遍历参数，可以使用循环：|1098608|for(var+i+=+arguments.length;+i--)+{
+++var+arg+=+arguments[i];
}|code-block|syntax|javascript|1098609|注意，arguments不是一个实数组，所以如果你需要它作为一个数组，你可以像这样转换它：|1098610|var+args+=+Array.prototype.slice.call(arguments);|1098611|entityMap^0|5|9|0|5|G|0|0|0|3|9|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|10|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|11|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|L|7|15|8|@]|D|@]|E|$M|N]]|$1|S|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|T|$]]

There is a hidden object passed to every function in JavaScript called <code>arguments</code>.

You would just use <code>arguments.length</code> to get the amount of arguments passed to the function.

To iterate through the arguments, you would use a loop:

<pre><code>for(var i = arguments.length; i--) {
 var arg = arguments[i];
}
</code></pre>

Note that <code>arguments</code> isn't a real array, so if you needed it as an array you would convert it like this:

<pre><code>var args = Array.prototype.slice.call(arguments);
</code></pre>

blocks|key|883713|text|arguments.length。您可以在其上使用for循环。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|883714|(function+()+{
++++for+(var+a+=+[],+i+=+arguments.length;+i--;)+{
++++++++a.push(arguments[i]);
++++};
++++return+a;
})(1,+2,+3,+4,+5,+6,+7,+8)|code-block|syntax|javascript|883715|entityMap^0|0|G|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

<code>arguments.length</code>. you can use a for loop on it.

<pre><code>(function () {
 for (var a = [], i = arguments.length; i--;) {
 a.push(arguments[i]);
 };
 return a;
})(1, 2, 3, 4, 5, 6, 7, 8)
</code></pre>

blocks|key|883865|text|现在对ES6来说好多了|type|unstyled|depth|inlineStyleRanges|entityRanges|data|883866|function+Example()+{
++++return+{
++++++++arguments:+(...args)+=>{
++++++++++++args.map(a+=>+console.log());
++++++++}
++++}
}

var+exmpl+=+new+Example();
exmpl.arguments(1,+2,+3,+'a',+'b',+'c');|code-block|syntax|javascript|883867|我希望这能帮到你|883868|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Much better now for ES6

<pre><code>function Example() {
 return {
 arguments: (...args) =&gt;{
 args.map(a =&gt; console.log());
 }
 }
}

var exmpl = new Example();
exmpl.arguments(1, 2, 3, 'a', 'b', 'c');
</code></pre>

I hope this helps

blocks|key|883886|text|ES6中的Rest参数|type|unstyled|depth|inlineStyleRanges|entityRanges|data|883887|const+example+=+(...args)+=>+{
++for+(arg+in+args)+{
++++console.log(arg);
++}
}|code-block|syntax|javascript|883888|注意:您可以在传递rest参数之前传入常规参数|883889|const+example+=+(arg1,+...args)+=>+{
++console.log(arg1);
++for+(arg+in+args)+{
++++console.log(arg);
++}
}|883890|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Rest parameters in ES6

<pre><code>const example = (...args) =&gt; {
 for (arg in args) {
 console.log(arg);
 }
}
</code></pre>

Note: you can pass regular parameters in before the rest params

<pre><code>const example = (arg1, ...args) =&gt; {
 console.log(arg1);
 for (arg in args) {
 console.log(arg);
 }
}
</code></pre>

blocks|key|883932|text|您可以使用展开/休息操作符创建函数，从那时起，您就实现了您的目标。请看下面的一大块。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|883933|const+print_names+=+(...args)+=>+args.forEach(x+=>+console.log(x));|code-block|syntax|javascript|883934|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|$]]

You can create a function using the spread/rest operator and from there on, you achieved your goal. Please take a look at the chunk below.

<pre><code>const print_names = (...args) =&gt; args.forEach(x =&gt; console.log(x));
</code></pre>

blocks|key|883974|text|您可以使用扩展/rest操作符将参数收集到一个数组中，然后该数组的length将是您传递的参数数量：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|883975|function+foo(...names)+{
++++console.log(names);
++++return+names;
}

console.log(foo(1,+2,+3,+4).length);|code-block|syntax|javascript|883976|我使用BabelJS将函数转换为老式的JS：|883977|"use+strict";

function+foo()+{
++for+(var+_len+=+arguments.length,+names+=+new+Array(_len),+_key+=+0;+_key+<+_len;+_key%2B%2B)+{
++++names[_key]+=+arguments[_key];
++}

++console.log(names);
++return+names;
}|883978|entityMap|0|LINK|mutability|MUTABLE|url|https://babeljs.io/repl#?babili=false&browsers=&build=&builtIns=false&spec=false&loose=false&code_lz=GYVwdgxgLglg9mABMOcAUA6LYCGBbAUwGcBKRAbwChEbEIEi4AbAjJuAczV0NIG5qtAE4EoIIUh7EBAX0pA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=true&fileSize=false&timeTravel=false&sourceType=module&lineWrap=true&presets=es2015%252Cstage-1&prettier=false&targets=&version=7.5.5&externalPlugins=^0|X|6|0|0|3|7|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|D|@$9|11|A|12|1|13]]|E|$]]|$1|M|3|N|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

You can use the spread/rest operator to collect your parameters into an array and then the <code>length</code> of the array will be the number of parameters you passed:

<pre><code>function foo(...names) {
 console.log(names);
 return names;
}

console.log(foo(1, 2, 3, 4).length);
</code></pre>

Using <a href="https://babeljs.io/repl#?babili=false&amp;browsers=&amp;build=&amp;builtIns=false&amp;spec=false&amp;loose=false&amp;code_lz=GYVwdgxgLglg9mABMOcAUA6LYCGBbAUwGcBKRAbwChEbEIEi4AbAjJuAczV0NIG5qtAE4EoIIUh7EBAX0pA&amp;debug=false&amp;forceAllTransforms=false&amp;shippedProposals=false&amp;circleciRepo=&amp;evaluate=true&amp;fileSize=false&amp;timeTravel=false&amp;sourceType=module&amp;lineWrap=true&amp;presets=es2015%2Cstage-1&amp;prettier=false&amp;targets=&amp;version=7.5.5&amp;externalPlugins=" rel="nofollow noreferrer">BabelJS</a> I converted the function to oldschool JS:

<pre><code>"use strict";

function foo() {
 for (var _len = arguments.length, names = new Array(_len), _key = 0; _key &lt; _len; _key++) {
 names[_key] = arguments[_key];
 }

 console.log(names);
 return names;
}
</code></pre>

blocks|key|883988|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|883989|let+x+=+function(){
++return+[].slice.call(arguments);
};

console.log(x('a','b','c','d'));|code-block|syntax|javascript|883990|883991|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|K|8|@]|9|@]|A|$E|F]]|$1|G|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|M|8|@]|9|@]|A|$]]]|I|$]]

<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>let x = function(){
 return [].slice.call(arguments);
};

console.log(x('a','b','c','d'));</code></pre>
</div>
</div>

blocks|key|1098661|text|我喜欢这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1098662|如果你不知道参数的数量，这不会有什么帮助，但如果你不想记住它们的顺序，它就会有帮助。|1098663|/**
+*++@param++params.one++++++++A+test+parameter
+*++@param++params.two++++++++Another+one++
+**/
function+test(params)+{

++++var+one+=+params.one;
++++if(typeof(one)+==+'undefined')+{
++++++++throw+new+Error('params.one+is+undefined');
++++}

++++var+two+=+params.two;
++++if(typeof(two)+==+'undefined')+{
++++++++throw+new+Error('params.two+is+undefined');
++++}
}|code-block|syntax|javascript|1098664|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I like to do this:

This will not help if you don't know the number of arguments, but it helps if you don't want to remember the order of them.

<pre><code>/**
 * @param params.one A test parameter
 * @param params.two Another one 
 **/
function test(params) {

 var one = params.one;
 if(typeof(one) == 'undefined') {
 throw new Error('params.one is undefined');
 }

 var two = params.two;
 if(typeof(two) == 'undefined') {
 throw new Error('params.two is undefined');
 }
}
</code></pre>

Is there a way to pass an unknown number of arguments like:

<pre><code>var print_names = function(names) {
 foreach(name in names) console.log(name); // something like this
}

print_names('foo', 'bar', 'baz');
</code></pre>

Also, how do I get the number of arguments passed in?

Pass unknown number of arguments into JavaScript function

是否有一种方法可以传递未知数量的参数，如：var print_names = function(names) {    foreach(name in names) console.log(name); // something like this}print_names('foo', 'bar', 'baz');另外，如何获取传入的参数数量？

问将未知数量的参数传递给JavaScript函数
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回答 10

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