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Cosmetic rewrite of String#startsWith and String#endsWith with performance-related comments.

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This commit is contained in:
Tobie Langel 2009-10-21 17:24:09 +02:00
parent 35ed99ba2e
commit 8783065b8e
1 changed files with 6 additions and 2 deletions
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8
src/lang/string.js
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@ -429,7 +429,9 @@ Object.extend(String.prototype, (function() {
* Checks if the string starts with `substring`.
**/
function startsWith(pattern) {
return !this.lastIndexOf(pattern,0);
// Using `lastIndexOf` instead of `indexOf` because execution time doesn't
// depend on string length.
return this.lastIndexOf(pattern, 0) === 0;
}
/**
@ -439,7 +441,9 @@ Object.extend(String.prototype, (function() {
**/
function endsWith(pattern) {
var d = this.length - pattern.length;
return d >= 0 && this.indexOf(pattern,d) === d;
// Using `indexOf` instead of `lastIndexOf` because execution time doesn't
// depend on string length.
return d >= 0 && this.indexOf(pattern, d) === d;
}
/**