65 lines
1.8 KiB
JavaScript
65 lines
1.8 KiB
JavaScript
|
/*---------------------------------------------------------------------------------------------
|
||
|
|
* Copyright (c) Microsoft Corporation. All rights reserved.
|
||
|
|
* Licensed under the MIT License. See License.txt in the project root for license information.
|
||
|
|
*--------------------------------------------------------------------------------------------*/
|
||
|
|
export function startsWith(haystack, needle) {
|
||
|
|
if (haystack.length < needle.length) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
for (let i = 0; i < needle.length; i++) {
|
||
|
|
if (haystack[i] !== needle[i]) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
/**
|
||
|
|
* Determines if haystack ends with needle.
|
||
|
|
*/
|
||
|
|
export function endsWith(haystack, needle) {
|
||
|
|
const diff = haystack.length - needle.length;
|
||
|
|
if (diff > 0) {
|
||
|
|
return haystack.lastIndexOf(needle) === diff;
|
||
|
|
}
|
||
|
|
else if (diff === 0) {
|
||
|
|
return haystack === needle;
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
/**
|
||
|
|
* @returns the length of the common prefix of the two strings.
|
||
|
|
*/
|
||
|
|
export function commonPrefixLength(a, b) {
|
||
|
|
let i;
|
||
|
|
const len = Math.min(a.length, b.length);
|
||
|
|
for (i = 0; i < len; i++) {
|
||
|
|
if (a.charCodeAt(i) !== b.charCodeAt(i)) {
|
||
|
|
return i;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return len;
|
||
|
|
}
|
||
|
|
export function repeat(value, count) {
|
||
|
|
let s = '';
|
||
|
|
while (count > 0) {
|
||
|
|
if ((count & 1) === 1) {
|
||
|
|
s += value;
|
||
|
|
}
|
||
|
|
value += value;
|
||
|
|
count = count >>> 1;
|
||
|
|
}
|
||
|
|
return s;
|
||
|
|
}
|
||
|
|
const _a = 'a'.charCodeAt(0);
|
||
|
|
const _z = 'z'.charCodeAt(0);
|
||
|
|
const _A = 'A'.charCodeAt(0);
|
||
|
|
const _Z = 'Z'.charCodeAt(0);
|
||
|
|
const _0 = '0'.charCodeAt(0);
|
||
|
|
const _9 = '9'.charCodeAt(0);
|
||
|
|
export function isLetterOrDigit(text, index) {
|
||
|
|
const c = text.charCodeAt(index);
|
||
|
|
return (_a <= c && c <= _z) || (_A <= c && c <= _Z) || (_0 <= c && c <= _9);
|
||
|
|
}
|