Question

我经常使用Array.prototype.filter而我只期望一个元素是真实的。

当过滤器返回结果数组时，我发现自己需要始终访问该元素，所以我做了类似的事情

knownRefundLogics.filter((refundLogic) => this.hasTag(refundLogic.underscoredName))[0]

假设：

knownRefundLogics = [{
    "underscoredName": "express_full_refund",
    "camelized": "expressFullRefund"
}, {
    "underscoredName": "express_partial_refund",
    "camelized": "expressPartialRefund"
}, {
    "underscoredName": "express_no_refund",
    "camelized": "expressNoRefund"
}]

和hasTag()在includes()元素的数组上执行refundLogic的方法。

是否有更合适的方法，例如使用扩展运算符？

顺便说一下，我知道我可能会以一种只返回true或false值的方式拆分我的方法，但我发现这是一种过度设计的解决方案。

Answer 1

使用Array#find（） - 只要谓词返回true，迭代就会停止，并且会立即返回匹配项（不是数组）：

const knownRefundLogics = [{"underscoredName":"express_full_refund","camelized":"expressFullRefund"},{"underscoredName":"express_partial_refund","camelized":"expressPartialRefund"},{"underscoredName":"express_no_refund","camelized":"expressNoRefund"}];

const demoHasTag = (t) => t === 'express_partial_refund';

const result = knownRefundLogics.find((refundLogic) => demoHasTag(refundLogic.underscoredName));

console.log(result);

Answer 2

您可以使用Array#find函数，该函数返回传递给定条件的第一个项目。此外，filter更快，因为filter遍历所有项目，然后您只获得第一个项目。 find找到第一个匹配的项目并打破循环。

从您可以看到的示例中，它迭代2次而不是3次。

const knownRefundLogics = [{
    "underscoredName": "express_full_refund",
    "camelized": "expressFullRefund"
}, {
    "underscoredName": "express_partial_refund",
    "camelized": "expressPartialRefund"
}, {
    "underscoredName": "express_no_refund",
    "camelized": "expressNoRefund"
}];

const foundItem = knownRefundLogics.find(item => {

   console.log('Iteration');
   
   return item.camelized === 'expressPartialRefund';

});

console.log(foundItem);

Answer 3

如果你想要一个没有polyfill的解决方案，好老的循环就是你的朋友。

＆＃13;

var knownRefundLogics = [{
    "underscoredName": "express_full_refund",
    "camelized": "expressFullRefund"
}, {
    "underscoredName": "express_partial_refund",
    "camelized": "expressPartialRefund"
}, {
    "underscoredName": "express_no_refund",
    "camelized": "expressNoRefund"
}];

var selected;
for(var i = 0; i < knownRefundLogics.length; i++){
  let current = knownRefundLogics[i];
  if(current.underscoredName === 'express_partial_refund'){
    selected = current;
    break;
  }
}

console.log(selected);

＆＃13;

这样你就可以编写自己的轻质填充物。

＆＃13;

function findInArray(array, test){
  for(var i = 0; i < array.length; i++){
    if(test(array[i], i, array)) return array[i];
  }
}

var knownRefundLogics = [{
    "underscoredName": "express_full_refund",
    "camelized": "expressFullRefund"
}, {
    "underscoredName": "express_partial_refund",
    "camelized": "expressPartialRefund"
}, {
    "underscoredName": "express_no_refund",
    "camelized": "expressNoRefund"
}];

console.log(findInArray(knownRefundLogics, function(item, index, array){
  return item.underscoredName === "express_partial_refund";
}));

＆＃13;

高效访问Array.prorotype.filter单项返回

3 个答案: