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This feature is well established and works across many devices and browser versions. Its been available across browsers since 2015 7.
concat() .
const str1 = "Hello";
const str2 = "World";
console.log(str1.concat(" ", str2));
// Expected output: "Hello World"
console.log(str2.concat(", ", str1));
// Expected output: "World, Hello"
str.concat(string2, string3[, ..., stringN])
.
concat() . . .
concat() .
var hello = "Hello, ";
console.log(hello.concat("Kevin", ". Have a nice day."));
/* Hello, Kevin. Have a nice day. */
var greetList = ["Hello", " ", "Venkat", "!"];
"".concat(...greetList); // "Hello Venkat!"
"".concat({}); // [object Object]
"".concat([]); // ""
"".concat(null); // "null"
"".concat(true); // "true"
"".concat(4, 5); // "45"
| Specification |
|---|
| ECMAScript 2027 LanguageSpecification # sec-string.prototype.concat |
This page was last modified on 2026 7 15 by MDN contributors.
StringString.prototype.anchor()String.prototype.at()String.prototype.big()String.prototype.blink()String.prototype.bold()String.prototype.charAt()String.prototype.charCodeAt()String.prototype.codePointAt()String.prototype.concat()String.prototype.endsWith()String.prototype.fixed()String.prototype.fontcolor()String.prototype.fontsize()String.prototype.includes()String.prototype.indexOf()String.prototype.isWellFormed()String.prototype.italics()String.prototype.lastIndexOf()String.prototype.link()String.prototype.localeCompare()String.prototype.match()matchAll()String.prototype.normalize()String.prototype.padEnd()String.prototype.padStart()String.prototype.repeat()String.prototype.replace()String.prototype.replaceAll()String.prototype.search()String.prototype.slice()String.prototype.small()String.prototype.split()String.prototype.startsWith()String.prototype.strike()String.prototype.sub()String.prototype.substr()String.prototype.substring()String.prototype.sup()String.prototype.toLocaleLowerCase()String.prototype.toLocaleUpperCase()String.prototype.toLowerCase()String.prototype.toString()String.prototype.toUpperCase()String.prototype.toWellFormed()String.prototype.trim()String.prototype.trimEnd()String.prototype.trimStart()String.prototype.valueOf()String.prototype[@@iterator]()Object/FunctionObject.prototype.__defineGetter__()Object.prototype.__defineSetter__()Object.prototype.__lookupGetter__()Object.prototype.__lookupSetter__()Object.prototype.hasOwnProperty()Object.prototype.isPrototypeOf()Object.prototype.propertyIsEnumerable()Object.prototype.toLocaleString()Object.prototype.toString()Object.prototype.valueOf()Your blueprint for a better internet.
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