Question by .call () method

Question

There is such a code

var abc = [1, 55, 399, 100].reduce(function(acc, el) { console.log('el= ' + el); acc += el; console.log('acc= ' + acc); return acc; }, 0); console.log('abc=' + abc); // el= 1 // acc= 1 // el= 55 // acc= 56 // el= 399 // acc= 455 // el= 100 // acc= 555 // abc=555

I don’t understand how to get access to each element of the array [1, 55, 399, 100] when calling the call () method and substituting the argument, let's say +10

 var abc = [1, 55, 399, 100].reduce.call(каждый_элемент_плюс_десять,function(acc, el) {} // или по другому в аргументе call должно быть такое [1, 55, 399, 100].forEach( function(element, index) { console.log(element+10); return element+10; });

Is it possible to do this without creating a pre-array to increase its values, and then substitute in reduce.call ()?

Without preforming an array, I mean this:

 var b = [1, 55, 399, 100]; var d = []; b.forEach( function(element, i) { d[i] = element+10; }); document.writeln(d +'<br>'); var abc = b.reduce.call(d, function(acc, el) { acc += el; return acc; }, 0); document.writeln('abc=' + abc);

The first call parameter is the context — in fact, for the reduce function — it must be an array or an ArrayLike object.
Therefore, it is not entirely clear what you are trying to do after all
Judging by the code, there is no need for a call at all, it suffices to return acc+el+10
@Grundy perhaps it was not important to increase the array element by 10, but rather to convert it on the fly, maybe +10, and maybe another action.

user207618 · Accepted Answer · 2016-04-13T01:28:15

How the call works.
In this case, the call applies to reduce , and you want to add an argument to the callback , right? Will not work.
call only changes this to reduce (and this does not need to be done, otherwise it will be an error) and can add currying to reduce , not to the callback .
Process the array with logic and then reduce it to one number.

 let array = [1, 55, 399, 100], newArray = array.map(e => e += 10).reduce((a, e) => {a += e; return a;}); document.writeln('Before: ' + array + '<br />'); document.writeln('After: &nbsp;&nbsp;' + newArray);

but this does not need to do, otherwise the error will be ?
jsfiddle.net/pqLj23eb/1 The error is not in JS, but in the expected behavior.
Although it is also possible to knock out an interpreter error if this is incorrect.
In the example of the link, the call itself changes its this and there is no error.
Well, call currying cannot add, because it returns no function
@Grundy There is no mistake you say ... i.stack.imgur.com/sCjlo.png About currying agree, there is a substitution only in place, Function.prototype.bind needed for full currying.

Question by .call () method

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