[英]Can arrow functions incorporate the multiple arguments of a host function such as reduce?
I assume the answer to this question is no, but I'm not sure. 我认为这个问题的答案是否定的,但我不确定。 Below is a reduce function , one is not using an arrow functions and one is.
下面是一个reduce函数,一个不使用箭头函数,一个是。 Is it possible to incorporate the second argument of the first into the arrow style ?
是否可以将第一个参数合并到箭头样式中?
var s = arr.reduce(function(){
},0) // includes second argument
and........ 和........
var a = arr.reduce = () => {
} // ?
Yes, Arrow functions can work with multiple params, they just need to be added inside parenthesis. 是的, 箭头函数可以使用多个参数,它们只需要在括号内添加。
var s = arr.reduce((accum, currVal) => accum + currVal, 0);
^ ^ : Multiple arguments to the Arrow function
^^^: Second argument of the `reduce` function
Here, the second parameter to the Array#reduce
can be passed normally. 这里,
Array#reduce
的第二个参数可以正常传递。 The arrow function( first parameter ) has no effect on how the second argument is passed. 箭头函数( 第一个参数 )对第二个参数的传递方式没有影响。
The part of this code: 这段代码的一部分:
var s = arr.reduce(function(){
},0) // includes second argument
...that an arrow function would replace is purely this bit: ...一个箭头函数将取代纯粹这一点:
function() {
}
Eg: 例如:
var s = arr.reduce(/*The function
goes
here*/,0) // includes second argument
The 0
is not related to the function being passed, it's a second argument to reduce
. 0
与传递的函数无关,它是reduce
的第二个参数。
So the equivalent of your first block is: 所以相当于你的第一个块是:
var s = arr.reduce(() => {
}, 0) // includes second argument
Although of course, if you're using reduce
, in both code blocks you're going to want some arguments: 虽然当然,如果你使用
reduce
,在两个代码块中你都会想要一些参数:
var s = arr.reduce(function(result, current) {
return /*...something combining `result` with `current`...*/;
}, 0);
So: 所以:
var s = arr.reduce((result, current) => {
return /*...something combining `result` with `current`...*/;
}, 0);
Or: 要么:
var s = arr.reduce((result, current) => /*...something combining `result` with `current`...*/, 0)
You have to call the host function as usual, and can supply multiple arguments as usual. 您必须像往常一样调用主机函数,并且可以像往常一样提供多个参数。 Just replace the function expression by the arrow function.
只需用箭头函数替换函数表达式即可。
var s = arr.reduce(() => {
…
}, 0);
Your second snippet did overwrite (assign to) arr.reduce
, not invoke it. 您的第二个片段覆盖(分配给)
arr.reduce
,而不是调用它。
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