CODEWITHSUNDEEP
javascript
Yasser Moussa
Yasser Moussa

Reputation: 2329

Dynamic variable name in loop

I need to create dynamic variable name in js inside for loop

var counter = 0;
for(i=0; i<location.length; i++) {
   ...
   var "marker_" + counter = new google.maps.Marker({

But when i expected to have variables marker_0,marker_1,marker_2,... i had this error

Error: SyntaxError: missing variable name
Source Code:
          var "marker_" + counter = new google.maps.Marker({

Upvotes: 2

Views: 7876

Answers (3)

T.J. Crowder
T.J. Crowder

Reputation: 1074148

Since this question is used as a duplicate target:

Use an array is good advice if the information you want to access is keyed numerically. If it isn't, you have two options:

  1. Use an object and dynamic property access

  2. Use a Map (ES2015+)

Using an object

You can access object properties using a string (or, in ES2015+, a Symbol) via brackets notation, so you can store information in an object to access later using strings/Symbols:

var theData = Object.assign(Object.create(null), {
    x: "ecks",
    y: "why"
});

var key = Math.random() < 0.5 ? "x" : "y";
console.log("key = " + key + ", theData[key] = " + theData[key]);

Using a Map

You can use a Map instead of an object even with strings or Symbols as keys, but unlike objects, Map keys can be any JavaScript value (except negative 0, but hey, good enough):

const theData = new Map([
    ["x", "ecks"],
    ["y", "why"]
]);

const key = Math.random() < 0.5 ? "x" : "y";
console.log("key = " + key + ", theData.get(key) = " + theData.get(key));

That example uses strings, but again, Map keys can be any type. A Map key can even be an object.

Upvotes: 0

Jamiec
Jamiec

Reputation: 136094

Well, "Use an array" is undoubtably the right answer here, however if you really want dynamic variables you need to decide the scope of them - the default would be window and then you could do this:

var counter = 0;
for(i=0; i<location.length; i++) {
   ...
   window["marker_" + counter] = new google.maps.Marker({

This can now be accessed with the same square bracket notation

window["marker_0"]...

or the dot notation

window.marker_0

Upvotes: 4

Explosion Pills
Explosion Pills

Reputation: 191729

Use an array:

var marker = [];

for (i=0; i < location.length; i++) {
   marker[counter] = new google.maps.Marker({

Upvotes: 11

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