String.prototype.startsWith()

Baseline

20159

startsWith() String true false

const str = "Saturday night plans";

console.log(str.startsWith("Sat"));
// : true

console.log(str.startsWith("Sat", 3));
// : false

startsWith(searchString)
startsWith(searchString, position)

searchString: str undefined startsWith() "undefined"
position: searchString searchString 0

searchString true false

TypeError: searchString

startsWith()

const str = "To be, or not to be, that is the question.";

console.log(str.startsWith("To be")); // true
console.log(str.startsWith("not to be")); // false
console.log(str.startsWith("not to be", 10)); // true


ECMAScript 2027 LanguageSpecification # sec-string.prototype.startswith

String.prototype.startsWith (core-js)
es-shims String.prototype.startsWith
String.prototype.endsWith()
String.prototype.includes()
String.prototype.indexOf()
String.prototype.lastIndexOf()

MDN

MDN 2025822

GitHub

String
1. String()
1. length
Object/Function
1. __proto__
2. constructor