Symbol.isConcatSpreadable
Symbol.isConcatSpreadable is a JavaScript property in the Symbol category. Indicates if an object should be flattened when using concat(). The syntax is Symbol.isConcatSpreadable. A typical example: const arr = [1,2]; arr[Symbol.isConcatSpreadable] = true. A close sibling is Symbol(), which creates a unique symbol. A close sibling is Symbol.for(), which looks up or creates a symbol in the global registry. A close sibling is Symbol.keyFor(), which returns the key of a global symbol. A close sibling is Symbol.prototype.toString(), which returns a string representation. More about this category: Symbol methods and properties. Related Symbol methods: Symbol(), Symbol.for(), Symbol.keyFor(), Symbol.prototype.toString(), Symbol.iterator, Symbol.asyncIterator, Symbol.hasInstance, Symbol.toStringTag. This page is part of the free JS Reference documentation covering 1027+ methods, each with syntax, parameters, return values, examples, and common pitfalls. You can try Symbol.isConcatSpreadable immediately in the JavaScript playground, look up unfamiliar terms in the glossary, or return to the JS Reference homepage.