blocks|key|670084|text|我将首先使用一元加号运算符将它们转换为数字。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|670085|%2Bnum1+%2B+%2Bnum2;|code-block|syntax|javascript|670086|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>I would use the unary plus operator to convert them to numbers first.   </p>

<pre><code>+num1 + +num2;
</code></pre>


blocks|key|669966|text|MDN+docs+for+parseInt|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|669967|MDN+docs+for+parseFloat|669968|在parseInt中，基数被指定为10，所以我们是以10为基数。在非严格javascript中，前面加上0的数字被视为八进制。这显然会带来问题！|style|CODE|669969|parseInt(num1,+10)+%2B+parseInt(num2,+10)+//base10
parseFloat(num1)+%2B+parseFloat(num2)|code-block|syntax|javascript|669970|另请参阅ChaosPandion的答案，以获得使用unary+operator的有用快捷方式。我已经设置了一个小提琴来显示不同的行为。|669971|http://jsfiddle.net/EtX6G/|669972|var+ten+=+'10';
var+zero_ten+=+'010';
var+one+=+'1';
var+body+=+document.getElementsByTagName('body')[0];

Append(parseInt(ten)+%2B+parseInt(one));
Append(parseInt(zero_ten)+%2B+parseInt(one));
Append(%2Bten+%2B+%2Bone);
Append(%2Bzero_ten+%2B+%2Bone);

function+Append(text)+{
++++body.appendChild(document.createTextNode(text));
++++body.appendChild(document.createElement('br'));
}|669973|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/parseInt|1|https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/parseFloat|2|http://xkr.us/articles/javascript/unary-add/|3^0|0|L|0|0|0|N|1|0|1G|1|0|0|P|E|2|0|0|Q|3|0|0^^$0|@$1|2|3|4|5|6|7|17|8|@]|9|@$A|18|B|19|1|1A]]|C|$]]|$1|D|3|E|5|6|7|1B|8|@]|9|@$A|1C|B|1D|1|1E]]|C|$]]|$1|F|3|G|5|6|7|1F|8|@$A|1G|B|1H|H|I]]|9|@]|C|$]]|$1|J|3|K|5|L|7|1I|8|@]|9|@]|C|$M|N]]|$1|O|3|P|5|6|7|1J|8|@]|9|@$A|1K|B|1L|1|1M]]|C|$]]|$1|Q|3|R|5|6|7|1N|8|@]|9|@$A|1O|B|1P|1|1Q]]|C|$]]|$1|S|3|T|5|L|7|1R|8|@]|9|@]|C|$M|N]]|$1|U|3|-4|5|6|7|1S|8|@]|9|@]|C|$]]]|V|$W|$5|X|Y|Z|C|$10|11]]|12|$5|X|Y|Z|C|$10|13]]|14|$5|X|Y|Z|C|$10|15]]|16|$5|X|Y|Z|C|$10|R]]]]

<p><a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/parseInt">MDN docs for parseInt</a>
<br />
<a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/parseFloat">MDN docs for parseFloat</a></p>

<p>In parseInt radix is specified as ten so that we are in base 10. In nonstrict javascript a number prepended with <code>0</code> is treated as octal. This would obviously cause problems!</p>

<pre><code>parseInt(num1, 10) + parseInt(num2, 10) //base10
parseFloat(num1) + parseFloat(num2)
</code></pre>

<p>Also see ChaosPandion's answer for a useful shortcut using a <a href="http://xkr.us/articles/javascript/unary-add/">unary operator</a>. I have set up a fiddle to show the different behaviors.</p>

<p><a href="http://jsfiddle.net/EtX6G/">http://jsfiddle.net/EtX6G/</a></p>

<pre><code>var ten = '10';
var zero_ten = '010';
var one = '1';
var body = document.getElementsByTagName('body')[0];

Append(parseInt(ten) + parseInt(one));
Append(parseInt(zero_ten) + parseInt(one));
Append(+ten + +one);
Append(+zero_ten + +one);

function Append(text) {
    body.appendChild(document.createTextNode(text));
    body.appendChild(document.createElement('br'));
}
</code></pre>


blocks|key|456041|text|我建议使用一元加号运算符，强制将最终的字符串作为数字，放在括号内，以使代码更具可读性，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|456042|(%2Bvarname)|code-block|syntax|javascript|456043|所以，在你的例子中是：|456044|var+num1+=+'20',
++++num2+=+'30.5';

var+sum+=+(%2Bnum1)+%2B+(%2Bnum2);

//+Just+to+test+it
console.log(+sum+);+//+50.5|456045|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|$]]

<p>I would recommend to use the unary plus operator, to force an eventual string to be treated as number, inside parenthesis to make the code more readable like the following:</p>

<pre><code>(+varname)
</code></pre>

<p>So, in your case it's:</p>

<pre><code>var num1 = '20',
    num2 = '30.5';

var sum = (+num1) + (+num2);

// Just to test it
console.log( sum ); // 50.5
</code></pre>


blocks|key|456052|text|var+result+=+Number(num1)+%2B+Number(num2);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|456053|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 result = Number(num1) + Number(num2);
</code></pre>


blocks|key|455790|text|使用parseFloat(string)将字符串转换为floats，或使用parseInt(string)将字符串转换为integers|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|455791|entityMap^0|2|I|R|6|11|G|1O|8|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|G|$]]

<p>convert the strings to <code>floats</code> with <code>parseFloat(string)</code> or to <code>integers</code> with <code>parseInt(string)</code></p>


blocks|key|670879|text|如果你需要将两个非常大的字符串相加，你需要计算每个字符串位置的加法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|670880|function+addStrings(str1,+str2){
++str1a+=+str1.split('').reverse();
++str2a+=+str2.split('').reverse();
++let+output+=+'';
++let+longer+=+Math.max(str1.length,+str2.length);
++let+carry+=+false;
++for+(let+i+=+0;+i+<+longer;+i%2B%2B)+{
++++let+result
++++if+(str1a[i]+&&+str2a[i])+{
++++++result+=+parseInt(str1a[i])+%2B+parseInt(str2a[i]);

++++}+else+if+(str1a[i]+&&+!str2a[i])+{
++++++result+=+parseInt(str1a[i]);

++++}+else+if+(!str1a[i]+&&+str2a[i])+{
++++++result+=+parseInt(str2a[i]);
++++}

++++if+(carry)+{
++++++++result+%2B=+1;
++++++++carry+=+false;
++++}
++++if(result+>=+10)+{
++++++carry+=+true;
++++++output+%2B=+result.toString()[1];
++++}else+{
++++++output+%2B=+result.toString();
++++}
++}
++output+=+output.split('').reverse().join('');

++if(carry)+{
++++output+=+'1'+%2B+output;
++}
++return+output;
}|code-block|syntax|javascript|670881|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>If you need to add two strings together which are very large numbers you'll need to evaluate the addition at every string position:</p>

<pre><code>function addStrings(str1, str2){
  str1a = str1.split('').reverse();
  str2a = str2.split('').reverse();
  let output = '';
  let longer = Math.max(str1.length, str2.length);
  let carry = false;
  for (let i = 0; i &lt; longer; i++) {
    let result
    if (str1a[i] &amp;&amp; str2a[i]) {
      result = parseInt(str1a[i]) + parseInt(str2a[i]);

    } else if (str1a[i] &amp;&amp; !str2a[i]) {
      result = parseInt(str1a[i]);

    } else if (!str1a[i] &amp;&amp; str2a[i]) {
      result = parseInt(str2a[i]);
    }

    if (carry) {
        result += 1;
        carry = false;
    }
    if(result &gt;= 10) {
      carry = true;
      output += result.toString()[1];
    }else {
      output += result.toString();
    }
  }
  output = output.split('').reverse().join('');

  if(carry) {
    output = '1' + output;
  }
  return output;
}
</code></pre>


blocks|key|670436|text|您可以使用此命令来添加数字：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|670437|var+x+=+%2Bnum1+%2B+%2Bnum2;|code-block|syntax|javascript|670438|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 use this to add numbers:</p>

<pre><code>var x = +num1 + +num2;
</code></pre>


blocks|key|456270|text|我一直都只是减去零。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|456271|num1-0+%2B+num2-0;|code-block|syntax|javascript|456272|假设一元运算符方法少了一个字符，但并不是每个人都知道一元运算符是什么，也不是每个人都知道当他们不知道它叫什么的时候如何谷歌来找出它。|456273|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|$]]

<p>I've always just subtracted zero.</p>

<pre><code>num1-0 + num2-0;
</code></pre>

<p>Granted that the unary operator method is one less character, but not everyone knows what a unary operator is or how to google to find out when they don't know what it's called.</p>


blocks|key|456644|text|function+sum(){
++++var+x,y,z;
++++x+=+Number(document.getElementById("input1").value);
++++y+=+Number(document.getElementById("input2").value);
++++z+=+x+%2B+y;
++++document.getElementById("result").innerHTML+=+z+;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|456645|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 sum(){
    var x,y,z;
    x = Number(document.getElementById("input1").value);
    y = Number(document.getElementById("input2").value);
    z = x + y;
    document.getElementById("result").innerHTML = z ;
}
</code></pre>


blocks|key|456586|text|如果您想以字符串形式对数字执行操作(例如，在数字大于64位的情况下)，您可以使用big-integer库。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|456587|const+bigInt+=+require('big-integer')
bigInt("999").add("1").toString()+//+output:+"1000"|code-block|syntax|javascript|456588|entityMap|0|LINK|mutability|MUTABLE|url|https://www.npmjs.com/package/big-integer^0|14|B|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>If you want to perform operation with numbers as strings (as in the case where numbers are bigger than 64bits can hold) you can use the <a href="https://www.npmjs.com/package/big-integer" rel="nofollow noreferrer">big-integer</a> library.</p>

<pre><code>const bigInt = require('big-integer')
bigInt("999").add("1").toString() // output: "1000"
</code></pre>


blocks|key|670144|text|您可以使用parseInt将字符串解析为数字。为了安全起见，始终将10作为要在基数10中解析的第二个参数传递。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|670145|num1+=+parseInt(num1,+10);
num2+=+parseInt(num2,+10);
alert(num1+%2B+num2);|code-block|syntax|javascript|670146|entityMap^0|5|8|X|2|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

<p>You can use <code>parseInt</code> to parse a string to a number. To be on the safe side of things, always pass <code>10</code> as the second argument to parse in base 10.</p>

<pre><code>num1 = parseInt(num1, 10);
num2 = parseInt(num2, 10);
alert(num1 + num2);
</code></pre>


blocks|key|670404|text|确保将最终结果四舍五入到浮点数的16位以下，因为java脚本有buggy。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|670405|例如5-+7.6+=+-2.5999999999999996|670406|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

<p>Make sure that you round your final answer to less than 16 decimal places for floats as java script is buggy.</p>

<p>For example
5 - 7.6 = -2.5999999999999996</p>


blocks|key|456745|text|@cr05s19xx建议回答重复的问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|456746|当涉及到数字和加法时，JavaScript有点搞笑。|456747|给出了以下内容|456748|'20‘-+'30’=+10；//以数字'20‘%2B+'30’=‘2030’的形式返回10；//以字符串的形式返回它们。从document.getElementById返回的值是字符串，所以在继续加法或减法之前，最好将它们全部(即使是有效的)解析为数字。您的代码可以是：|456749|function+myFunction()+{
++var+per+=+parseInt(document.getElementById('input1').value);
++var+num+=+parseInt(document.getElementById('input2').value);
++var+sum+=+(num+/+100)+*+per;
++var+output+=+num+-+sum;

++console.log(output);

++document.getElementById('demo').innerHTML+=+output;
}

function+myFunction2()+{
++var+per+=+parseInt(document.getElementById('input3').value);
++var+num+=+parseInt(document.getElementById('input4').value);
++var+sum+=+(num+/+100)+*+per;
++var+output+=+sum+%2B+num;

++console.log(output);

++document.getElementById('demo1').innerHTML+=+output;
}|code-block|syntax|javascript|456750|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|R|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|S|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

<p>@cr05s19xx suggested on a duplicate question:</p>

<p>JavaScript is a bit funny when it comes to numbers and addition.</p>

<p>Giving the following</p>

<p>'20' - '30' = 10; // returns 10 as a number
'20' + '30' = '2030'; // Returns them as a string
The values returned from document.getElementById are strings, so it's better to parse them all (even the one that works) to number, before proceeding with the addition or subtraction. Your code can be:</p>

<pre><code>function myFunction() {
  var per = parseInt(document.getElementById('input1').value);
  var num = parseInt(document.getElementById('input2').value);
  var sum = (num / 100) * per;
  var output = num - sum;

  console.log(output);

  document.getElementById('demo').innerHTML = output;
}

function myFunction2() {
  var per = parseInt(document.getElementById('input3').value);
  var num = parseInt(document.getElementById('input4').value);
  var sum = (num / 100) * per;
  var output = sum + num;

  console.log(output);

  document.getElementById('demo1').innerHTML = output;
}
</code></pre>


blocks|key|670186|text|使用parseFloat方法将字符串解析为浮点数：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|670187|parseFloat(num1)+%2B+parseFloat(num2)|code-block|syntax|javascript|670188|entityMap^0|2|A|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|$]]

<p>Use the <code>parseFloat</code> method to parse the strings into floating point numbers:</p>

<pre><code>parseFloat(num1) + parseFloat(num2)
</code></pre>


blocks|key|456442|text|我在我的项目中使用它，我使用%2B号将字符串作为数字处理(在with_interesst变量中)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|456443|<script>
function+computeLoan(){
var+amount+=+document.getElementById('amount').value;
var+interest_rate+=+document.getElementById('interest_rate').value;
var+days+=+document.getElementById('days').value;
var+interest+=+(amount+*+(interest_rate+*+.01))+/+days;
var+payment+=+((amount+/+days)+%2B+interest).toFixed(2);
var+with_interest+=+(amount+*+(interest_rate+*+.01));
var+with_interesst+=+(%2Bamount+*+(interest_rate+*+.01))+%2B+(%2Bamount);
payment+=+payment.toString().replace(/\B(?=(\d{3})%2B(?!\d))/g,+",");
document.getElementById('payment').innerHTML+=+"Target+Daily+=+PHP"%2Bpayment;
document.getElementById('with_interesst').innerHTML+=+"Amount+w/Interest+=+++PHP"%2Bwith_interesst;
}
</script>

<div+name="printchatbox"+id="printchatbox">
+<form+id="Calculate"+class="form-horizontal">
+++<h2>You+Can+Use+This+Calculator+Before+Submit+</h2>
+++<p>Loan+Amount:+PHP<input+id="amount"+type="number"+min="1"+max="1000000"++onchange="computeLoan()"></p>
+++<p>Interest+Rate:+<input+id="interest_rate"+type="number"+min="0"+max="100"+value="10"+step=".1"+onchange="computeLoan()">%25</p>
++++<p>Term<select+id="days"+type="number"+min="1"+max="72"+step=".1"+onchange="computeLoan()">
++++<option+value="40">40+Days</option>
++++<option+value="50">50+Days</option>
++++<option+value="60">60+Days</option>
++++<option+value="70">70+Days</option>
++++<option+value="80">80+Days</option>
++++<option+value="90">90+Days</option>
++++<option+value="100">100+Days</option>
++++<option+value="120">120+Days</option>
++++</select>
++++</p>++++++++++++++++++++++++
+++<h2+id="payment"></h2>
+++<h2+id+="with_interesst"></h2>
+</form>
</div>|code-block|syntax|javascript|456444|希望能有所帮助|456445|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|$]]

<p>I use this in my project.I use + sign to treat string as a number (in with_interesst variable)</p>

<pre><code>&lt;script&gt;
function computeLoan(){
var amount = document.getElementById('amount').value;
var interest_rate = document.getElementById('interest_rate').value;
var days = document.getElementById('days').value;
var interest = (amount * (interest_rate * .01)) / days;
var payment = ((amount / days) + interest).toFixed(2);
var with_interest = (amount * (interest_rate * .01));
var with_interesst = (+amount * (interest_rate * .01)) + (+amount);
payment = payment.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
document.getElementById('payment').innerHTML = "Target Daily = PHP"+payment;
document.getElementById('with_interesst').innerHTML = "Amount w/Interest =   PHP"+with_interesst;
}
&lt;/script&gt;

&lt;div name="printchatbox" id="printchatbox"&gt;
 &lt;form id="Calculate" class="form-horizontal"&gt;
   &lt;h2&gt;You Can Use This Calculator Before Submit &lt;/h2&gt;
   &lt;p&gt;Loan Amount: PHP&lt;input id="amount" type="number" min="1" max="1000000"  onchange="computeLoan()"&gt;&lt;/p&gt;
   &lt;p&gt;Interest Rate: &lt;input id="interest_rate" type="number" min="0" max="100" value="10" step=".1" onchange="computeLoan()"&gt;%&lt;/p&gt;
    &lt;p&gt;Term&lt;select id="days" type="number" min="1" max="72" step=".1" onchange="computeLoan()"&gt;
    &lt;option value="40"&gt;40 Days&lt;/option&gt;
    &lt;option value="50"&gt;50 Days&lt;/option&gt;
    &lt;option value="60"&gt;60 Days&lt;/option&gt;
    &lt;option value="70"&gt;70 Days&lt;/option&gt;
    &lt;option value="80"&gt;80 Days&lt;/option&gt;
    &lt;option value="90"&gt;90 Days&lt;/option&gt;
    &lt;option value="100"&gt;100 Days&lt;/option&gt;
    &lt;option value="120"&gt;120 Days&lt;/option&gt;
    &lt;/select&gt;
    &lt;/p&gt;                        
   &lt;h2 id="payment"&gt;&lt;/h2&gt;
   &lt;h2 id ="with_interesst"&gt;&lt;/h2&gt;
 &lt;/form&gt;
&lt;/div&gt;
</code></pre>

<p>Hope it helps</p>


blocks|key|671108|text|document.getElementById(currentInputChoosen).value+-=+%2B-100;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|671109|在我的情况下，如果你遇到和我一样的问题，但找不到解决方案，就会发现这个问题。|unstyled|671110|很抱歉有点离题，但我刚刚发现这是有效的，我认为它可能是值得分享的。|671111|不知道这是一个肮脏的变通方法，还是实际上是合法的。|671112|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|F|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>document.getElementById(currentInputChoosen).value -= +-100;
</code></pre>

<p>Works in my case, if you run into the same problem like me and can't find a solution for that case and find this SO question.</p>

<p>Sorry for little bit off-topic, but as i just found out that this works, i thought it might be worth sharing.</p>

<p>Don't know if it is a dirty workaround, or actually legit.</p>


blocks|key|456512|text|您可以像这样使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|456513|var+num1+=+'20',
++++num2+=+'30.5';

alert((num1*1)+%2B+(num2*1));+//result+50.5|code-block|syntax|javascript|456514|在num1中应用*1时，将字符串转换为数字。|456515|如果num1包含字母或逗号，则返回NaN乘以1|456516|如果num1为null，则num1返回0|456517|致以良好的问候！|456518|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

<p>You may use like this:</p>

<pre><code>var num1 = '20',
    num2 = '30.5';

alert((num1*1) + (num2*1)); //result 50.5
</code></pre>

<p>When apply *1 in num1, convert string a number.</p>

<p>if num1 contains a letter or a comma, returns NaN multiplying by 1 </p>

<p>if num1 is null, num1 returns 0</p>

<p>kind regards!!!</p>


blocks|key|670362|text|如果您正在寻找简单的Javascript代码，并希望使用两个输入框并从两个值中添加数字，请尝试此方法。这是代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|670363|++++Enter+the+first+number:+<input+type="text"+id="num1"+/><br+/>
++++Enter+the+seccond+number:+<input+type="text"+id="num2"+/><br+/>
++++<input+type="button"+onclick="call()"+value="Add"/>

++++<script+type="text/javascript">
++++function+call(){
++++var+q=parseInt(document.getElementById("num1").value);
++++var+w=parseInt(document.getElementById("num2").value);
++++var+result=q%2Bw;
++++}
++++</script>|code-block|syntax|javascript|670364|欲了解更多详情，请访问http://informativejavascript.blogspot.nl/2012/12/javascript-basics.html。|offset|length|670365|entityMap|0|LINK|mutability|MUTABLE|url|http://informativejavascript.blogspot.nl/2012/12/javascript-basics.html^0|0|0|B|1Z|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

<p>Try this if you are looking for simple Javascript code and want to use two input box and add numbers from the two value. Here's the code.</p>

<pre><code>    Enter the first number: &lt;input type="text" id="num1" /&gt;&lt;br /&gt;
    Enter the seccond number: &lt;input type="text" id="num2" /&gt;&lt;br /&gt;
    &lt;input type="button" onclick="call()" value="Add"/&gt;

    &lt;script type="text/javascript"&gt;
    function call(){
    var q=parseInt(document.getElementById("num1").value);
    var w=parseInt(document.getElementById("num2").value);
    var result=q+w;
    }
    &lt;/script&gt;
</code></pre>

<p>for more details please visit <a href="http://informativejavascript.blogspot.nl/2012/12/javascript-basics.html" rel="nofollow">http://informativejavascript.blogspot.nl/2012/12/javascript-basics.html</a></p>


<p>I have two strings which contain only numbers:</p>

<pre><code>var num1 = '20',
    num2 = '30.5';
</code></pre>

<p>I would have expected that I could add them together, but they are being concatenated instead:</p>

<pre><code>num1 + num2; // = '2030.5'
</code></pre>

<p>How can I force these strings to be treated as numbers?</p>


How to add two strings as if they were numbers?

我有两个只包含数字的字符串：var num1 = '20',    num2 = '30.5';我本以为我可以将它们加在一起，但它们却被连接在一起：num1 + num2; // = '2030.5'如何强制将这些字符串视为数字？

问如何将两个字符串相加，就像它们是数字一样？
EN

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问如何将两个字符串相加，就像它们是数字一样？EN

回答 18

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问如何将两个字符串相加，就像它们是数字一样？
EN