How to add together numerical values that are stored in strings?

Question

I'm trying to add 1 to my JavaScript variable, but the following code doesn't give expected results:

var val1 = document.getElementById('<%= rng1.ClientID %>');
var val2 = val1.value + "1";
alert(val2.value);

How can I do this?

Answer 1

parseInt($('.scpContainer').height()+200)

Answer 2

you can use the function parseInt() to transform the string stored in val1.value into a number:

var val2 = parseInt(val1.value) + 1;

Note that Number(val1.value) will also convert your value into a number.

-edit-
As yc suggest, is highly recommended to use parseInt(val1.value, 10) + 1; because if your string starts with a "0" the string is interpreted as octal. eg. parseInt("0123") == 83 and not 123

Answer 3

The simplest and also preferred way would be to use + to cast to a number.

Examples:

+'234'; // 234
+'042'; // 42! It does not convert to octal

In your case:

var val1 = +(document.getElementById('<%= rng1.ClientID %>').value); // () added just for the looks
var val2 = val1.value + 1; // if val1 is 5, val2 will be 6 hooray!
alert(val2); // just val2, since it's a plain number not an html input element