问题描述
我正在浏览bacon.js幻灯片:
在第二个街区的第一行,它说:
pre $ 函数always(value){返回函数(_){返回值}}
function(_)是什么意思?
由于JavaScript没有进行参数计数检查,所以参数可能被完全省略。这种丢弃标识符在其他语言中更常见,但应考虑类似于 arr.forEach(function(_,i){..})的情况,其中 _ 表示不使用第一个参数。
I'm going through the bacon.js slide at:http://raimohanska.github.io/bacon.js-slides/1.html
In the 1st line of the 2nd block, it says:
function always(value) { return function(_) { return value } }
what does function(_) mean?
In this case _ is just a function parameter - a single underscore is a convention used by some programmers to indicate "ignore this binding/parameter".
Since JavaScript doesn't do parameter-count checking the parameter could have been omitted entirely. Such a "throw-away" identifier is found more commonly in other languages, but consider a case like arr.forEach(function (_, i) {..}) where _ indicates the first parameter is not to be used.
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