Tag Archives: EcmaScript 6

EcmaScript 6 – String.prototype.repeat()

One simple function that is on the roster to be released in EcmaScript 6 is String.prototype.repeat. The following can be used to define it in browsers which don’t currently have it defined natively:

String.prototype.repeat = String.prototype.repeat || function(count) {
    return Array(count >= 0 ? parseInt(count, 10) + 1 : -1).join(this);

Here are some examples of using this function (modified from the originals found on MDN):

alert("->".repeat(-1));     // RangeError
alert("->".repeat(0));      // ""
alert("->".repeat(1));      // "->"
alert("->".repeat(2));      // "->->"
alert("->".repeat(3.6));    // "->->->" (count will be converted to integer)
alert("->".repeat(1/0));    // RangeError

There is more information about this new JavaScript function here.

EcmaScript 6 – Math.sign()

One function I didn’t think would be doable in most browsers was the Math.sign. My main worry was that on the MDN page it specifies a difference between negative zero and positive zero. After doing some research I found this page which helped me realize there is a way to determine if you are dealing with normal zero or negative zero. With that in mind, my proposed definition for Math.sign is as follows:

Math.sign = Math.sign || function(n) {
  return (n = +n) ? n < 0 ? -1 : 1 : n;

As far as I can tell, this JavaScript function definition is a good equivalent to make the function available on browsers that dont yet natively provide this feature. Have fun! 8-)

EcmaScript 6 – Array.of()

A function that is proposed to be added to EcmaScript 6 is Array.of(). This function will be used to create an array of the passed parameters. Since this function is available in some browsers but not in all, here is a block of code which when executed will define it if not already defined:

Array.of = Array.of || function() {
  return Array.prototype.slice.call(arguments);

Here are some examples of using the function:

var a = Array.of(1,2,3);     // [1,2,3]
var b = Array.of();          // []
var c = Array.of(undefined); // [undefined]
var d = Array.of(null);      // [null]
var e = Array.of(4);         // [4]

Not the most amusing function, but it is still a step towards EcmaScript 6. 8-)