Again, it is just like in the confusing case of Array methods (see my previous blog post on JavaScript Array: slice vs splice)

var c = 'The Three Musketeers' Įach of these three function can accept two parameters and perform the string extraction based on those parameter values. In other words, it follows what is expected for Array’s slice in the same situation and thus it returns an empty string instead. If the end value is smaller than the start, slice will not internally swap the values.

For all intents and purposes, slice has a behavior very close to substring (accepting start and end position). To add more confusion to this mixture, a String object also supports slice ( Section 15.5.4.13), just like in Array’s slice. Without looking at the documentation or the specification, there is a chance of picking a wrong one. It also does not help that the names, substring and substr, are too similar. It is so easy to mistake one for another and thereby leading to an unexpected outcome. This pair of functions, when they are both available, can be really confusing. This is shown in the following fragment: var b = 'The Three Musketeers' However, the parameters for substr are the start character position and the numbers of characters to be extracted, respectively. Many JavaScript environments (including most modern web browsers) also implement a variant of substring called substr ( Section B.2.3). An example of substring is illustrated in this code snippet: var a = 'The Three Musketeers' In case the end value is smaller than the start, substring is smart enough to swap the values before doing the string extraction. This substring function can accept two numbers, the start and the end (exclusive) character position, respectively. String’s substring (ECMAScript 5.1 Specification Section 15.5.4.15) is the first logical choice to retrieve a part of the string. Even worse, sometimes it is easy to fall into the trap and choose the wrong function. Because of this, often it is very confusing for beginners as to which function should be used. With JavaScript, there are three different built-in functions which can perform that operation. Ariya.io About Talks Articles JavaScript String: substring, substr, sliceĮxtracting a portion of a string is a fairly well understood practice.

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