Can not pass variable on function using jQuery .then()

Asked Feb 13 '20 at 21:40

Active Feb 13 '20 at 21:40

Viewed 28 times

I have jQuery loading a json, and I am using .then() notation to run a function doThis() when the json is ready. However, if I pass a variable on doThis(), it returns 'undefined'.

I figured out this much: In my application the jQuery gets run on mouse click, and when passing a variable, it does run on second mouse click. Seems like the json gets loaded, but jQuery does not wait for the json to finish loading if I pass a variable.

This works:

$.getJSON('/endpoint/', function(data) {
  data = data
})
  .then(doThis)

This does not work even with no variable in the parenthesis:

$.getJSON('/endpoint/', function(data) {
  data = data
})
  .then(doThis())

I am sure this has something to do with the architecture of JavaScript. Would be awesome if someone could enlighten me a little.

Thanks in advance!

asked Feb 13 '20 at 21:40

andrus

3

Because the `then()` expects a callback. Unless `doThis()` returns a function, you're not giving it a callback in the second instance. – Taplar Feb 13 '20 at 21:41
You need `.then(function () { doThis(someValue); });` – Feb 13 '20 at 21:43
Could also use `bind()` – Taplar Feb 13 '20 at 21:45
It's actually: `.then(function (data) { doThis(data, someOtherValue); });` (or: `then(doThis.bind(this, data))`) – Feb 13 '20 at 21:49
That solved it, thanks! – andrus Feb 26 '20 at 17:36

Can not pass variable on function using jQuery .then()

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