An example to pass an array of params to those composed functions, . /* Store function names and match params */
let at = {
at_26 : (a,b,c) => at_26(a,b,c),
at_21 : (a,b,c) => at_21(a,b,c),
at_99 : (a,b,c) => at_99(a,b,c),
at_om : (a,b,c,d,e) => at_om(a,b,c,d,e)
}
/* Dynamic function router: name + array of Params */
function dynFunc(name, arrayParams){
return at[name](...arrayParams)
}
/* Usage examples */
dynFunc(`at_${99}`, ["track001", 32, true])
dynFunc("at_" + "om", ["track007", [50, false], 7.123, false, "Bye"])
/* In the scope */
function at_99(a,b,c){
console.log("Hi! " + a,b,c)
console.log(typeof(a), typeof(b), typeof(c))
}
function at_om(a,b,c,d,e){
console.log("Hi! " + a,b,c,d,e)
console.log(typeof(a), typeof(b), typeof(c), typeof(d), typeof(e))
} A Function object's read-only name property indicates the function's name as specified when it was created, or it may be either anonymous or '' (an empty string) for functions created anonymously. Try itNote: In non-standard, pre-ES2015 implementations the configurable attribute was false as well. DescriptionThe function's name property can be used to identify the function in debugging tools or error messages. It has no semantic significance to the language itself. The name property is read-only and cannot be changed by the assignment operator: function someFunction() {}
someFunction.name = 'otherFunction';
console.log(someFunction.name); // someFunction
To change it, use
Object.defineProperty() . The name property is typically inferred from how the function is defined. In the following sections, we will describe the various ways in which it can be inferred. Function declarationThe name property returns the name of a function declaration. function doSomething() {}
doSomething.name; // "doSomething"
Default-exported function declarationAn export default declaration exports the function as a declaration instead of an expression. If the declaration is
anonymous, the name is "default" . // -- someModule.js --
export default function () {};
// -- main.js --
import someModule from "./someModule.js";
someModule.name; // "default"
Function constructorFunctions created with the
Function() constructor have name "anonymous". new Function().name; // "anonymous"
Function expression
If the function expression is named, that name is used as the name property. const someFunction = function someFunctionName() {};
someFunction.name; // "someFunctionName"
Anonymous function expressions created using the keyword function or arrow functions would have "" (an empty string) as their name. (function () {}).name; // ""
(() => {}).name; // ""
However, such cases are rare — usually, in order to refer to the expression elsewhere, the function expression is attached to an identifier when it's created (such as in a variable declaration). In such cases, the name can be
inferred, as the following few subsections demonstrate. One practical case where the name cannot be inferred is a function returned from another function: function getFoo() {
return () => {};
}
getFoo().name; // ""
Variable declaration and methodVariables and methods can infer the name of an anonymous function from its syntactic position. const f = function () {};
const object = {
someMethod: function () {}
};
console.log(f.name); // "f"
console.log(object.someMethod.name); // "someMethod"
The same applies to assignment: let f;
f = () => {};
f.name; // "f"
Initializer and default valueFunctions in initializers (default values) of destructuring,
default parameters, class fields, etc., will inherit the name of the bound identifier as their name . const [f = () => {}] = [];
f.name; // "f"
const { someMethod: m = () => {} } = {};
m.name; // "m"
function foo(f = () => {}) {
console.log(f.name);
}
foo(); // "f"
class Foo {
static someMethod = () => {};
}
Foo.someMethod.name; // someMethod
Shorthand methodconst o = {
foo() {},
};
o.foo.name; // "foo";
Bound functionFunction.prototype.bind() produces a function whose name is "bound " plus the function name.
function foo() {};
foo.bind({}).name; // "bound foo"
Getter and
setterWhen using get and set accessor properties, "get" or "set" will appear in the function name. const o = {
get foo() {},
set foo(x) {},
};
const descriptor = Object.getOwnPropertyDescriptor(o, "foo");
descriptor.get.name; // "get foo"
descriptor.set.name; // "set foo";
ClassA class's name follows the same algorithm as function declarations and expressions. class Foo {}
Foo.name; // "Foo"
Warning: JavaScript will set the function's name property only if a function does not have an own property called name . However, classes'
static members will be set as own properties of the class constructor function, and thus prevent the built-in name from being applied. See an example below. Symbol as function nameIf a Symbol is used a function name and the symbol has a description, the
method's name is the description in square brackets. const sym1 = Symbol("foo");
const sym2 = Symbol();
const o = {
[sym1]() {},
[sym2]() {},
};
o[sym1].name; // "[foo]"
o[sym2].name; // "[]"
Private propertyPrivate fields and private methods have the hash (# ) as part of their names. class Foo {
#field = () => {};
#method() {}
getNames() {
console.log(this.#field.name);
console.log(this.#method.name);
}
}
new Foo().getNames();
// "#field"
// "#method"
Telling the constructor name of an objectYou can use obj.constructor.name to check the "class" of an object. function Foo() {} // Or: class Foo {}
const fooInstance = new Foo();
console.log(fooInstance.constructor.name); // logs "Foo"
However, because static members will become own properties of the class, we can't obtain the class name for virtually any class with a
static method property name() : class Foo {
constructor() {}
static name() {}
}
With a static name() method Foo.name no longer holds the actual class name but a reference to the name() function object. Trying to obtain the class of fooInstance via fooInstance.constructor.name won't give us the class name at all, but instead a reference to the static class method. Example: const fooInstance = new Foo();
console.log(fooInstance.constructor.name); // logs function name()
Due to the existence of static fields, name may not be a function either. class Foo {
static name = 123;
}
console.log(new Foo().constructor.name); // 123
If a class has a static property called
name , it will also become writable. The built-in definition in the absence of a custom static definition is read-only: Foo.name = 'Hello';
console.log(Foo.name); // logs "Hello" if class Foo has a static name() property but "Foo" if not.
Therefore you may not rely on the built-in name property to always hold a class's name. JavaScript compressors and minifiersWarning: Be careful when using the name property with source-code transformations, such as those carried out by JavaScript compressors (minifiers) or obfuscators. These tools are often used as part of a JavaScript
build pipeline to reduce the size of a program prior to deploying it to production. Such transformations often change a function's name at build time. Source code such as: function Foo() {};
const foo = new Foo();
if (foo.constructor.name === 'Foo') {
console.log("'foo' is an instance of 'Foo'");
} else {
console.log('Oops!');
}
may be compressed to: function a() {};
const b = new a();
if (b.constructor.name === 'Foo') {
console.log("'foo' is an instance of 'Foo'");
} else {
console.log('Oops!');
}
In the uncompressed version, the program runs into the truthy branch and logs "'foo' is an instance of 'Foo'" — whereas, in the compressed version it behaves differently, and runs into the else branch. If you rely on the name property, like in the
example above, make sure your build pipeline doesn't change function names, or don't assume a function has a particular name. Specifications
Specification |
---|
ECMAScript Language Specification # sec-function-instances-name
|
Browser compatibilityBCD tables only load in the browser See also- A polyfill for functions'
.name property is available in core-js Function
Is a function name a variable?
yes. drive will be a variable whose value is a named function with the same name. The compiler declares the variable for you, gives it a named function as the value of it -and with the same name as the variable-, and also hoists the variable.
Can a function be stored as a variable in JavaScript?
In JavaScript, functions are called Function Objects because they are objects. Just like objects, functions have properties and methods, they can be stored in a variable or an array, and be passed as arguments to other functions.
Can variable name and function name be same JavaScript?
Variables and functions share the same namespace in JavaScript, so they override each other. if function name and variable name are same then JS Engine ignores the variable. With var a you create a new variable. The declaration is actually hoisted to the start of the current scope (before the function definition).
Can you assign a function to a variable in JavaScript?
1.1 A regular function
It is possible to use a function expression and assign it to a regular variable, e.g. const factorial = function(n) {...} .
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