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javascriptnode.jsecmascript-5

string.startsWith() Wildcard OR Regular Expression

Refactoring some code that uses string.startsWith() in JavaScript. Docs don't say you can use wildcard or Regular Expression. What is alternative?

Solution

  • string.prototype.match and regex.prototype.test.

    'string'.match(/regex/):

    let a = 'hello'.match(/^[gh]/); // truthy (['h'])
let b = 'gello'.match(/^[gh]/); // truthy (['g'])
let c = 'ello'.match(/^[gh]/); // falsey (null)
console.log(a, b, c);

    /regex/.test('string'):

    let a = /^[gh]/.test('hello'); // true
let b = /^[gh]/.test('gello'); // true
let c = /^[gh]/.test('ello'); // false
console.log(a, b, c);

    The regex symbol ^ ensures the regex matches only at the string start.