ES6 – Convert To Integer

There are various ways to convert a string or a floating point number to an integer in JavaScript, but not all of them may suit your needs. In this post we will examine four different ways and then we will see which is the best in all cases.

Solution #1: ~~x

If we are dealing with smaller number then we can leverage bit-wise operators such as bit-wise negation (~). The reason we can only use this solution for smaller numbers is because bit-wise operations can only be executed on a number in the range of -(231) to 231 - 1. If the number is outside of that range it will be converted to a number within that range (eg. -2147483649 becomes 2147483647 and 2147483648 becomes -2147483648).

Solution #2: parseInt(x, 10)

There is actually a function that will convert strings into numbers called parseInt(). We can use this function and specify the base to ensure that numbers starting with 0 will not be parsed as octals (eg. parseInt('010') produces 8 in older versions of ECMAScript).

Solution #3: +parseFloat(x, 10).toFixed(0)

We can also use the equivalent function to parseInt() for floats which is parseFloat(). After that we can use Number.prototype.toFixed() to make the number a string representation of the truncated number. Finally we can prefix this expression with a plus sign (+) to convert the string to a number again.

Solution #4: Math.trunc(x)

We can use the newer Math.trunc() function which should in theory just do what we want 😆 .


Below are the results of using your browser to test out each solution:


    If you have looked through the results above on a modern browser (one implementing Math.trunc()) you’ll notice that for all of our test cases, it is the only solution that works for them all. Therefore, if you are looking to convert floating-point numbers to integers or strings to integers, the most convenient and straightforward way may in fact be ES6’s new Math.trunc() function. Let me know what you think and as always, happy coding! 😎

    JavaScript Snippet – isValidVarName()

    Now Available in YourJS

    Recently I was working on a function which needed to determine whether or not a string could be used as a variable name. Variable name validation can get tricky so instead of using a crazy regular expression which includes all keywords (which may change over time) and instead of testing for strange unicode characters which are rarely used for variable names, I decided to leverage the JavaScript Function constructor:

    The above function takes the string in question and returns true if the string can be used a variable name. If the string can not be used as a variable name false is returned.

    Some may wonder why I’m doing the following:

    varName.replace(/[\s\xA0,\/]|^$/g, '.')

    The reason I included the above replacement is to avoid false-positives in the case of an empty string, extra spacing, commas, and forward slashes.


    Others have attempted to make the same function using the evil eval() function which allows for JS injection. Even though the Function constructor can also be used for evil, when supplying arguments it does prevent you from doing JS injection by making sure the arguments don’t have parentheses.


    The following is an example of what will happen when running for the function for a number of strings:

    console.log(isValidVarName(''));           // -> false
    console.log(isValidVarName('3'));           // -> false
    console.log(isValidVarName('3d'));          // -> false
    console.log(isValidVarName('D3'));          // -> true
    console.log(isValidVarName('D3 '));         // -> false
    console.log(isValidVarName('D3,Q'));        // -> false
    console.log(isValidVarName('D3/*Qs*/'));   // -> false
    console.log(isValidVarName('D3Q'));         // -> true
    console.log(isValidVarName('var'));         // -> false
    console.log(isValidVarName('true'));        // -> false
    console.log(isValidVarName('undefined'));   // -> true
    console.log(isValidVarName('null'));        // -> false
    console.log(isValidVarName('coolio.pop'));  // -> false
    console.log(isValidVarName('coolio'));      // -> true
    console.log(isValidVarName('coolio_pop'));  // -> true
    console.log(isValidVarName('$'));           // -> true
    console.log(isValidVarName('$á'));          // -> true
    console.log(isValidVarName('áÑ'));          // -> true
    console.log(isValidVarName('_'));           // -> true

    Here is a similar example hosted on JSBin:
    JS Bin on