Determine in JavaScript whether an array includes a function in its elements

Question

Determine in JavaScript whether an array includes a function in its elements

Currently, I am adding anonymous functions to an array in the following manner:

myArray.push(function(){ /* some unique code here */});
myArray.push(function(){ /* even more unique code here */});

Afterwards, I execute all the functions by doing

while (myArray.length) { myArray.shift().call();}

The query at hand is: How can I determine if a function already exists in myArray? I attempted using toSource() for comparison, but unfortunately, it did not yield the desired result... Any suggestions?

Appreciate any insight provided ahead of time.

javascript arrays function

Answer 1

Answer №1

Compare the functions by converting them to strings:

func1.toString() === func2.toString()

Even anonymous functions can be compared this way, as long as you are looking for exact matches in code.

Answer 2

Compare the functions by converting them to strings:

func1.toString() === func2.toString()

Even anonymous functions can be compared this way, as long as you are looking for exact matches in code.

Answer 3

Answer №2

One way to verify if a function is present in an array is by using the Array.prototype.indexOf method:

var func1 = function () {};
var func2 = function () {};
var myArray = [];

var checkFunction = function (func) {
    if (myArray.indexOf(func) === -1) {
        myArray.push(func);
    }
};

checkFunction(func1);
checkFunction(func1);
console.log(myArray.indexOf(func1));    // outputs 0
console.log(myArray.indexOf(func2));    // outputs -1

Alternatively, you can utilize a map object to determine if a function has been added or not:

var funct1 = function funct1() {};
var funct2 = function funct2() {};
var myArr = [];
var myMap = {};

var addFunc = function (fn) {
    if (!myMap[fn.name]) {
        myArr.push(fn);
        myMap[fn.name] = fn;
    }
};

addFunc(funct1);
addFunc(funct1);
console.log(myArr.indexOf(funct1), myMap['funct1']);    // shows 0, function funct1() { ... }
console.log(myArr.indexOf(funct2), myMap['funct2']);    // shows -1, undefined

Note: This second approach may not be suitable for anonymous functions.

Answer 4

One way to verify if a function is present in an array is by using the Array.prototype.indexOf method:

var func1 = function () {};
var func2 = function () {};
var myArray = [];

var checkFunction = function (func) {
    if (myArray.indexOf(func) === -1) {
        myArray.push(func);
    }
};

checkFunction(func1);
checkFunction(func1);
console.log(myArray.indexOf(func1));    // outputs 0
console.log(myArray.indexOf(func2));    // outputs -1

Alternatively, you can utilize a map object to determine if a function has been added or not:

var funct1 = function funct1() {};
var funct2 = function funct2() {};
var myArr = [];
var myMap = {};

var addFunc = function (fn) {
    if (!myMap[fn.name]) {
        myArr.push(fn);
        myMap[fn.name] = fn;
    }
};

addFunc(funct1);
addFunc(funct1);
console.log(myArr.indexOf(funct1), myMap['funct1']);    // shows 0, function funct1() { ... }
console.log(myArr.indexOf(funct2), myMap['funct2']);    // shows -1, undefined

Note: This second approach may not be suitable for anonymous functions.

Answer 5

Answer №3

While compiling functions into the list, maintain a separate entity where you log a unique identifier to ensure whether the function has already been included in the array:

  var myList = [], functionLog = {};
  for (var x = 0; x < someLimit; ++x) {
     // carry out necessary actions
     if (certainCondition) {
       if (!functionLog[ "example code 1" ]) {
         myList.push(function() { /* example code 1 */ });
         functionLog[ "example code 1" ] = true;
       }
     }

     if (anotherCondition) {
       if (!functionLog[ "example code 2" ]) {
         myList.push(function() { /* example code 2 */ });
         functionLog[ "example code 2" ] = true;
       }
     }
  }

Answer 6

While compiling functions into the list, maintain a separate entity where you log a unique identifier to ensure whether the function has already been included in the array:

  var myList = [], functionLog = {};
  for (var x = 0; x < someLimit; ++x) {
     // carry out necessary actions
     if (certainCondition) {
       if (!functionLog[ "example code 1" ]) {
         myList.push(function() { /* example code 1 */ });
         functionLog[ "example code 1" ] = true;
       }
     }

     if (anotherCondition) {
       if (!functionLog[ "example code 2" ]) {
         myList.push(function() { /* example code 2 */ });
         functionLog[ "example code 2" ] = true;
       }
     }
  }

Determine in JavaScript whether an array includes a function in its elements

Answer №1

Answer №2

Answer №3

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