I am trying to understand how can we achieve such a function in JS, and what is the main use of this approach?
multiple(5) will return 5 multiple(5)(6) will return 30
how can we achieve such a function in JavaScript?
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5Hint: `multiple` will return a function – John Dvorak Feb 11 '18 at 12:00
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Welcome to Stack Overflow! Please take the [tour] and read through the [help], in particular [*How do I ask a good question?*](/help/how-to-ask) Do your research, [search](/help/searching) for related topics on SO, and give it a go. ***If*** you get stuck and can't get unstuck after doing more research and searching, post a [mcve] of your attempt and say specifically where you're stuck. People will be glad to help. Good luck! – T.J. Crowder Feb 11 '18 at 12:03
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4"currying" is the keyword for you. – oniondomes Feb 11 '18 at 12:04
1 Answers
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You can use valueOf and function that return a function.
Here: multiple(5) will return 5 multiple(5)(6) will return 30
function multiple(x){
function func(y){
return x*y
}
func.valueOf=function(){return x}
return func
}
See this JSFiddle: https://jsfiddle.net/k9meraL6/
alert(multiple(5)(6)) //30
alert(multiple(5) + 1) //6
More info:
Valueof
JavaScript calls the valueOf method to convert an object to a primitive value
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf
Aminadav Glickshtein
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1If your answer is downvoted, deleting it and reposting it is **not** the correct response. *(not my dv)* – T.J. Crowder Feb 11 '18 at 12:06
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T.J. Crowder, Your right, It was by mistake, I edited the question, and instead, it created a new answer, so I have to delete one of my answers. Anyway, You are welcome to downvote it again. – Aminadav Glickshtein Feb 11 '18 at 12:07
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4*"I edited the question, and instead it created a new answer"* Eight years and more on SO, never once has the site magically decided that an edit was a new answer. – T.J. Crowder Feb 11 '18 at 12:08
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2@oniondomes: So that `multiply(5)` would seem to give the value 5 while really returning a function. – T.J. Crowder Feb 11 '18 at 12:08
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T.J.Crowder, after years here on SO it never happened to me either, today after editing a question, I clicked the "back" button of the browser, and it goes back to editing a question, but when I posted it, it created a new answer. – Aminadav Glickshtein Feb 11 '18 at 12:10
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1@Aminadav: Even **if** that's true (and I find it very hard to believe with a site like SO), so you delete the new one. Whatever. Moving on. – T.J. Crowder Feb 11 '18 at 12:11
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@T.J.Crowder it returning a function but it behaves like a number in calculations. – Aminadav Glickshtein Feb 11 '18 at 12:16
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Right. That's what I said above when oniondomes asked why you were using it. – T.J. Crowder Feb 11 '18 at 12:18