JavaScript: Dynamically Creating Variables for Loops [duplicate]

Question

This question already has answers here:

How do I create dynamic variable names inside a loop? (9 answers)

Closed last year.

How can I use a for loop to dynamically create variables, and be returned.

function createVariables()
{
for ( i=0; i<=20; i++ )
 {
 var account = i;
 return var account + i;
 }
 }

The goal is to have the result below:

var account1;
var account2;
var account3; and etc.....

Answer 1

You should use an array:

function createVariables(){
 var accounts = [];
 for (var i = 0; i <= 20; ++i) {
 accounts[i] = "whatever";
 }
 return accounts;
}

You then have access to accounts[0] through accounts[20].

• spacedev: idea is to create variables with the strings we have... e.g., I have array var arr = ['myOwnName']; and from this create a variable called , var myOwnName
• leun4m: You cannot create dynamically new variables, but you might consider using a Map for this purpose

Answer 2

The only way I know how to do this would be to use the JavaScript eval function.

Something like eval("account" + 1 + "='some value'");

http://www.w3schools.com/jsref/jsref_eval.asp

However, I think @Domenic has a better answer.

• ThickMiddleManager: His answer only is good if you know what variables you will need.

Answer 3

I was unsure about answering an old question however I stumbled across this while seeking an answer myself.

for (var i = 1; i < 11; i++) { // Creating 10 objects
window["Object"+i] = new Object();
}
console.log(Object7); // is not undefined

The above code loops to 10 while creating dynamic objects, as described on https://www.codecademy.com/en/forum_questions/51068e93f73ad4947a005629

• Buraco: Absolutely much better than eval() recommandation above. Thanks!
• Roman: absolutely not better, node.js doesn't know what window is. Question is about js, nowhere is specified that this only should work in a browser

Answer 4

I find this a simplest solution

for (var i = 0; i < 10; i++) {
 this["RONAK"+i] = "MY VAL";
}

Output

RONAK0 = "MY VAL"
RONAK1 = "MY VAL"
RONAK2 = "MY VAL"
...
RONAK9 = "MY VAL"

Answer 5

You can use the eval() method to declare dynamic variables as it executes JavaScript statements passed to it.

function createVariables()
{
 for ( i=0; i<=20; i++ )
 {
 var str ="account"+ i+" = undefined";
 //Declaring and Setting dynamic variable to undefined using eval
 eval(str);
 }
}
createVariables();

Answer 6

let etc = { name: 'foobar', city: 'xyz', company: 'companyName' };
Object.keys(etc).forEach(key=>{
window[`${key.toUpperCase()}`] = new Object(`${etc[`${key}`]}`)
});
console.log("-->"+NAME) //foobar

this is similar to what @whatevermike describes but it does not work in NodeJS because it uses window. :(

Answer 7

function createVariables() {
 var accounts = [];
 for (var i = 0; i <= 20; ++i) {
 accounts[i] = "merhaba" + i;
 }
 return accounts;
}

• Charles: It would be helpful to add an explanation along with your code, so that OP and others can better understand it.

Answer 8

The following code will actually create variables, instead of creating this sort of hash table proposed by @Domenic

 function createVariables(){
 var varName = "accounts";
 for (var i = 0; i <= 20; ++i) {
 eval('var ' + varName + i + ' = ' + '"whatever"' + ';');
 }
 return accounts;
 }

Answer 9

I was pretty proud of the way I made iterating variables with my code, was going to share it but I think I'll just sort of show you modified version of it.

function variableBuilder() {
 let i = 0;
 while (i <= 20) {
 let accountVariable = "account".concat(i);
 `// variable can even be reassigned here`
 console.log(accountVariable);
 i++;
 }
}

you can use the variable as an iterating variable identifier, in the spot that I suggested; I used this method to build DOM nodes, to create a dynamically built HTML table.

Answer 10

we can use map for it.

var map = {};
for (var i = 0; i < 10; ++i) {
 map["nutrient" + i] = "some stuff" + i;
}
console.log(map)

result:

{
 nutrient0: 'some stuff0',
 nutrient1: 'some stuff1',
 nutrient2: 'some stuff2',
 nutrient3: 'some stuff3',
 nutrient4: 'some stuff4',
 nutrient5: 'some stuff5',
 nutrient6: 'some stuff6',
 nutrient7: 'some stuff7',
 nutrient8: 'some stuff8',
 nutrient9: 'some stuff9'
}

Answer 11

the easiest method is to use eval and write the variable declaration line inside a loop that follows your conditions

 for (let i = 0; i <= 3; i++) {
 eval(`var variable${i}=${i}`);
 eval(`console.log(variable${i})`)
 }
//Output:
0
1
2
3

You can also console log the values outside as they are declared global with the var keyword

Answer 12

ES6 Method

const dyVars = 7;
for (let i = 0; i < dyVars; i++){
 eval(`var dynamicVar${i+1} = '${i+1} variable created';`);
 console.log(eval(`dynamicVar${i+1}`));
}