i have the following Html
<input class="top-display" value="5+5" id="display" disabled="disabled"> </input>
<button class="btn" > submit </button>
And jquery
$('.btn').click(function(){
var selected = $('#display').val();
alert(selected);
});
fiddle Here my focus for this code is letting jquery to automatically do the math for me. like instead of jquery alerting "5+5" it should alert "10". and if the value = "5-5" is should alert "0"; without adding any if statement.
The eval() method evaluates JavaScript code represented as a string.
Change your code to this:
$('.btn').click(function(){
var selected = eval($('#display').val());
alert(selected);
});
Also note:
eval() is a dangerous function, which executes the code it's passed with the privileges of the caller.
Read more at MDN to understand the risks involving eval.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval
$('.btn').click(function(){
var selected = $('#display').val();
alert(eval(selected));
});
Don't forget to add proper error handling to avoid errors in the situations where there are in compatible values.
Edit:
The eval function has known security vulnerabilities. It is always advisable not to use it.
$('.btn').click(function(){
var selected = $('#display').val();
alert(evil(selected));
});
function evil(fn) {
return new Function('return ' + fn)();
}
This is another solution I found in another thread.
Reason why you are getting 5+5 in alert is because your 'expression' is not executed. Where eval(args) will execute the arguments.
eval() can be used in this case as long as you sanitize the input string like below:
$('.btn').click(function(){
// strip anything other than digits, (), -+/* and .
var selected = $('#display').val().replace(/[^-()\d/*+.]/g, '');
alert(eval(selected ));
});
You can also refer to this thread for other alternatives to eval(). The security risks of using eval() has been discussed here in great detail.
Cheers!
EDIT: Updated fiddle link here for testing.
$('#display').val()toeval($('#display').val()). Although Eval can be dangerous. Make sure you read about it and understand it.