String.prototype.startsWith()

The startsWith() method of {{jsxref("String")}}  values determines whether this string begins with the characters of a specified string, returning true or false as appropriate.

{{InteractiveExample("JavaScript Demo: String.prototype.startsWith()")}} 

const str = "Saturday night plans";

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

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

Syntax

startsWith(searchString)
startsWith(searchString, position)

Parameters

• searchString
  • : The characters to be searched for at the start of this string. Cannot be a regex. All values that are not regexes are coerced to strings, so omitting it or passing undefined causes startsWith() to search for the string "undefined", which is rarely what you want.
• position {{optional_inline}} 
  • : The start position at which searchString is expected to be found (the index of searchString’s first character). Defaults to 0.

Return value

true if the given characters are found at the beginning of the string, including when searchString is an empty string; otherwise, false.

Exceptions

• {{jsxref("TypeError")}} 
  • : Thrown if searchString is a regex.

Description

This method lets you determine whether or not a string begins with another string. This method is case-sensitive.

Examples

Using 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

Specifications

{{Specifications}} 

Browser compatibility

{{Compat}} 

See also

• Polyfill of String.prototype.startsWith in core-js
• es-shims polyfill of String.prototype.startsWith
• {{jsxref("String.prototype.endsWith()")}} 
• {{jsxref("String.prototype.includes()")}} 
• {{jsxref("String.prototype.indexOf()")}} 
• {{jsxref("String.prototype.lastIndexOf()")}}