Lodash _.startsWith() Method

What You’ll Learn

By the end of this tutorial, you’ll use Lodash’s _.startsWith() confidently in real JavaScript projects.

What Is _.startsWith()?

_.startsWith() checks whether a string begins with a given prefix. It is ideal for input validation, filtering arrays of filenames, and guarding URL or protocol formats.

📝 Syntax

_.startsWith(string, target, [position=0])

Syntax Rules

• string — The string to inspect.
• target — Prefix substring to find at the start (from position).
• position — Optional index to begin searching (default 0).
• Return — Boolean true if prefix matches.
• Case — Case-sensitive unless you normalize case first.

import startsWith from "lodash/startsWith";

const str = "Hello, world!";
const ok = startsWith(str, "Hello");
// -> true

Examples Gallery

Practical _.startsWith() patterns with sample output and interactive Try It Yourself labs.

const str = "Hello, world!";
const prefix = "Hello";
const startsWithPrefix = _.startsWith(str, prefix);

console.log(startsWithPrefix);
// -> true

startsWithPrefix: true

const str = "Hello, world!";
const prefix = "world";

const match = _.startsWith(str, prefix, 7);
// position 7 -> "world!..."

console.log(match);
// -> true

match: true

function isValidUrl(url) {
  return _.startsWith(url, "http://") || _.startsWith(url, "https://");
}

console.log(isValidUrl("https://example.com"));
// -> true

isValidUrl("https://example.com"): true

const str = "Hello, World!";
const prefix = "hello";

const ok = _.startsWith(_.toLower(str), _.toLower(prefix));
// -> true

ok: true

const files = ["app.js", "index.html", "app.test.js"];
const jsApps = files.filter(function (f) {
  return _.startsWith(f, "app");
});
// -> ["app.js", "app.test.js"]

jsApps: ["app.js", "app.test.js"]

const s = "Hello";

console.log(_.startsWith(s, "He"));
console.log(s.startsWith("He"));
// both -> true

Both: true

📝 Notes

• Comparison is case-sensitive—normalize with _.toLower() when needed.
• Use position to test prefixes mid-string, not only at index 0.
• For suffix checks, use _.endsWith().
• Returns false when target is longer than the remaining substring.
• Validate types in public APIs before relying on coercion.