Dynamically create object keys in IE 11 (Expected identifier, string or number, not a comma issue)

Question

I'm looking for a solution that creates object keys (is that worded correctly?) dynamically.

Arbitrary example, but this works in chrome and firefox

var weeks = {}
for(var i = 0; i < 5; i++){
    $.extend(weeks, {["week" + i] : (i * 2)}
}

//weeks = {"week0":0,"week1":2,"week2":4,"week3":6,"week4":8}

Or alternative arbitrary example

var object = {
  ["a" + 50]: "value"
}

The problem seem to be rooted in the [] operator, but I don't understand how or why this problem only occurs in IE. I have not tested in previous versions to IE11, but I would assume the problem would persist there aswell.

Since the problem seem to be with the [] operator itself, creating my keys in a variable and then shoving that variable into my [] wouldn't do anything to fix the problem, so I seem to be both out of ideas and keywords to google.

So is there a way to dynamically create object keys in IE?

Answer 1

IE11 is not a "modern" web browser in the same way Chrome, Firefox or even Edge is. It doesn't support the new "object literal extensions" from ES6 (ES2015).

The syntax you are using is called "computed property keys", you cannot use it in IE11. You need to do this the "old fashioned" way.

var weeks = {};

for(var i = 0; i < 5; i++){
    var tmp = {};
    tmp["week" + i] = i*2;

    $.extend(weeks, tmp);
}