什么是序列的Python'枚举'的ES6等价物？

Python has a built-in function enumerate, to get an iterable of (index, item) pairs.

Python有一个内置函数枚举,以获得(index,item)对的可迭代。

Does ES6 have an equivalent for an array? What is it?

ES6是否具有数组的等价物?它是什么?

def elements_with_index(elements):
    modified_elements = []
    for i, element in enumerate(elements):
         modified_elements.append("%d:%s" % (i, element))
    return modified_elements

print(elements_with_index(["a","b"]))
#['0:a', '1:b']

ES6 equivalent without enumerate:

ES6等效而不枚举:

function elements_with_index(elements){
     return elements.map(element => elements.indexOf(element) + ':' + element);
 }

console.log(elements_with_index(['a','b']))
//[ '0:a', '1:b' ]

6 个解决方案

#1

Yes there is, check out Array.prototype.entries().

是的,请查看Array.prototype.entries()。

#2

Array.prototype.map already gives you the index as the second argument to the callback procedure... And it's supported almost everywhere.

Array.prototype.map已经将索引作为回调过程的第二个参数......并且几乎在任何地方都支持它。

['a','b'].map(function(element, index) { return index + ':' + element; });
//=> ["0:a", "1:b"]

I like ES6 too

我也喜欢ES6

['a','b'].map((e,i) => `${i}:${e}`)
//=> ["0:a", "1:b"]

#3

Excuse me if I'm being ignorant (bit of a newbie to JavaScript here), but can't you just use forEach? e.g:

对不起,如果我对此无知(这里是JavaScript的新手),但是你不能只使用forEach吗?例如:

function withIndex(elements) {
    var results = [];
    elements.forEach(function(e, ind) {
        results.push(`${e}:${ind}`);
    });
    return results;
}

alert(withIndex(['a', 'b']));

There's also naomik's answer which is a better fit for this particular use case, but I just wanted to point out that forEach also fits the bill.

还有naomik的答案,它更适合这个特定的用例,但我只是想指出forEach也符合要求。

ES5+ supported.

#4

let array = [1, 3, 5];
for (let [index, value] of array.entries()) 
     console.log(index + '=' + value);

#5

pythonic offers an enumerate function that works on all iterables, not just arrays, and returns a generator (yield), like python:

pythonic提供了一个枚举函数,适用于所有迭代,而不仅仅是数组,并返回一个生成器(yield),如python:

import {enumerate} from 'pythonic';

const arr = ['a', 'b'];
for (const [index, value] of enumerate(arr))
    console.log(`index: ${index}, value: ${value}`);
// index: 0, value: a
// index: 1, value: b

#6

as Kyle and Shanoor say is Array.prototype.entries()

正如Kyle和Shanoor所说的是Array.prototype.entries()

but for newbie like me, hard to fully understand its meaning.

但对于像我这样的新手,很难完全理解它的含义。

so here give an understandable example:

所以这里给出一个可以理解的例子:

for(let curIndexValueList of someArray.entries()){
  console.log("curIndexValueList=", curIndexValueList)
  let curIndex = curIndexValueList[0]
  let curValue = curIndexValueList[1]
  console.log("curIndex=", curIndex, ", curValue=", curValue)
}

equivalent to python code:

相当于python代码:

for curIndex, curValue in enumerate(someArray):
  print("curIndex=%s, curValue=%s" % (curIndex, curValue))
}

#1