unexpected token ( for javascript

Question

I want to write an algorithm into javascript and I am sure I wrote true . the algorithm gives a number from user and gives the user the result : 1+3+5+...+(2n+1) and "n" is var. the javascript gives me errors : calc() is not defined , unexpected token;

<html>
<head>
    <title>Algorithm</title>
    <script type="text/javascript">
        function calc(){
            var n = document.getElementById('value').value;
            var sum = 0, i = 1, k = 0;
            for(k=0,k<n,k++){
            sum = sum += i;
            i+=2;
            k++;
            }
            document.getElementById('answer').innerHTML = sum;
        }
    </script>
</head>
<body>
    <input type="text" id="value" placeholder="Enter your number"/>
    <button onclick="calc()">OK</button><br/>
    <h1 id="answer"></h1>
</body>

In the for loop header, you should use ; instead of ,: for(k=0;k<n;k++){ — Sirko
– Sirko, Commented Aug 3, 2014 at 8:05
Possible duplicate of for loop causing "Unexpected token" error — Léon Pelletier
– Léon Pelletier, Commented Nov 20, 2017 at 22:37

Lix · Accepted Answer · 2014-08-03 08:04:58Z

4

The problem is your for loop syntax. You need to use a semi-colon ; to separate the statements:

for( k = 0; k < n; k++ ){
 ...
}

Taken from the MDN documentation:

Creates a loop that consists of three optional expressions, enclosed in parentheses and separated by semicolons, followed by a statement executed in the loop.

The JavaScript engine can not parse your for loop and then it encounters the closing bracket of the loop (which it wasn't expecting as it was still trying to parse the conditions of the loop).

answered Aug 3, 2014 at 8:04

Lix

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Comments

Ask Bjørn Hansen · Accepted Answer · 2014-08-03 08:04:48Z

2

The for() statement needs semicolons (;) instead of commas (,).

for (var k=0; k < n; k++) {

The "jshint" tool can be very helpful in catching mistakes in javascript. There's a web version of it on jshint.com

answered Aug 3, 2014 at 8:04

Ask Bjørn Hansen

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Zaenille · Accepted Answer · 2014-08-03 08:04:58Z

1

for(k=0,k<n,k++){

You're using commas instead of semicolons.

answered Aug 3, 2014 at 8:04

Zaenille

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Mritunjay · Accepted Answer · 2014-08-03 08:05:52Z

1

That is because you should have ; instead of , in for syntax.

for(k=0;k<n;k++){...}

answered Aug 3, 2014 at 8:05

Mritunjay

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Comments

Kyle Emmanuel · Accepted Answer · 2014-08-03 08:10:30Z

0

Your for statement is using commas instead of semi-colons. Change it to use ;.

for(k=0,k<n,k++){
    sum = sum += i;
    i+=2;
    k++;
}

answered Aug 3, 2014 at 8:10

Kyle Emmanuel

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