convert string to integer and calculate

Question

I am making a calculator which will work as follows:
the user will put his calculation in a textbox eg: 2+4+5; then the whole string will be converted to integer and calculate the numbers and display the result:11;. My code is as follows:

Script:

function solve() {  
    problem = parseInt(document.getElementById('prob'));   
    ans = document.getElementById('ansspace');  
    ans.innerHTML = problem  
}

HTML:

<input type="text" id="prob">  
<br>  <input type="button" id="add" value="Add" onclick="solve()">  <br>  
<p id='ansspace'></p>

What is your question? If it's about how to evaluate the string, this has been asked before. — Felix Kling
– Felix Kling, Commented Jun 9, 2012 at 17:08

ThiefMaster · Accepted Answer · 2012-06-09 17:18:01Z

2

You can use eval() to do calculation, but beware of security issues. eval is not recommended as user can execute his code from page. Otherwise, use regex to parse the content or use regex to validate if input values are safe to use with eval

edited Jun 9, 2012 at 17:18

ThiefMaster

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answered Jun 9, 2012 at 17:12

hungryMind

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1 Comment

ThiefMaster Over a year ago

Code injection is a non-issue in this case as the user could also do so by running a javascript: url in the address bar, using his browser's developer tools, etc. As long as he cannot share a link to the calculation (i.e. get other users to execute whatever he entered) this is not a big problem. Using try..catch to do proper error handling is fine for this.

jacktheripper · Accepted Answer · 2012-06-09 17:23:21Z

1

Using jQuery as simple as:

$('#add').on('click', function() {
    var solution = eval($('#prob').val());
    $('#ansspace').html(solution);
});

See a live example here

edited Jun 9, 2012 at 17:23

answered Jun 9, 2012 at 17:17

jacktheripper

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3 Comments

ThiefMaster Over a year ago

While I'm all pro-jQuery and you do answer the question I don't think it was really necessary to rewrite his code to use jQuery. By the way, .on('click' ...) is the preferred way to go since jQuery 1.7.

jacktheripper Over a year ago

Thanks for the heads up! I did not know the standard had changed :)

Mahesh Bansod Over a year ago

thanks for your answer but i dont want to use jquery and i dont know any programming of it, can you give the answer in Javascript

WojtekT · Accepted Answer · 2012-06-09 17:28:02Z

0

There's really no easy way to make an calculator but for your code to work you can use eval:

function solve() {  
  var problem = document.getElementById('prob').value;   
  var ans = document.getElementById('ansspace');   
  ans.innerHTML = eval(problem);  
}

edited Jun 9, 2012 at 17:28

answered Jun 9, 2012 at 17:12

WojtekT

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1 Comment

ThiefMaster Over a year ago

Please do not create unnecessary globals. Use var to make variables local.

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