# Functions — Function expressions

> While the function declaration above is syntactically a statement, functions can also be created by a function expression.

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- Canonical URL: <https://wikikv.com/k/ref-mdn-343b184939a0ccbdba9d>
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- Updated: `2026-08-16T09:31:44.535576+00:00`
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## Knowledge

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While the function declaration above is syntactically a statement, functions can also be created by a function expression.

Such a function can be anonymous; it does not have to have a name. For example, the function square could have been defined as

However, a name _can_ be provided with a function expression. Providing a name allows the function to refer to itself, and also makes it easier to identify the function in a debugger's stack traces

Function expressions are convenient when passing a function as an argument to another function. The following example defines a map function that should receive a function as first argument and an array as second argument. Then, it is called with a function defined by a function expression

In JavaScript, a function can be defined based on a condition. For example, the following function definition defines myFunc only if num equals 0

In addition to defining functions as described here, you can also use the {{jsxref("Function")}} constructor to create functions from a string at runtime, much like {{jsxref("Global_Objects/eval", "eval()")}}.

A method is a function that is a property of an object. Read more about objects and methods in Working with objects.

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