The Function
constructor creates a new Function
object. Calling the constructor directly can create functions dynamically, but suffers from security and similar (but far less significant) performance issues to eval
. However, unlike eval, the Function
constructor creates functions which execute in the global scope only.
Syntax
new Function([arg1 [, arg2 [, ...argN]] ,] functionBody)
Parameters
arg1, arg2, ... argN
- Names to be used by the function as formal argument names. Each must be a string that corresponds to a valid JavaScript identifier, or a list of such strings separated with a comma. For example: "
x
", "theValue
"—or "x,theValue
". functionBody
- A string containing the JavaScript statements comprising the function definition.
Description
Function
objects created with the Function
constructor are parsed when the function is created. This is less efficient than declaring a function with a function expression or function statement and calling it within your code because such functions are parsed with the rest of the code.
All arguments passed to the function are treated as the names of the identifiers of the parameters in the function to be created, in the order in which they are passed. Omitting an argument will result in the value of that parameter being undefined
.
Invoking the Function
constructor as a function (without using the new
operator) has the same effect as invoking it as a constructor.
Examples
Specifying arguments with the Function constructor
The following code creates a Function
object that takes two arguments.
// Example can be run directly in your JavaScript console // Create a function that takes two arguments, and returns the sum of those arguments const adder = new Function('a', 'b', 'return a + b'); // Call the function adder(2, 6); // 8
The arguments "a
" and "b
" are formal argument names that are used in the function body, "return a + b
".
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Function constructor' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Function() constructor | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 4 | Opera Full support 3 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
Legend
- Full support
- Full support
See also
- Functions and function scope
function
statementfunction
expressionfunction*
statementfunction*
expressionAsyncFunction
GeneratorFunction