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javascript - 在 JavaScript 中过滤对象数组？

问题描述

以下程序过滤给定的对象数组并返回一个包含满足条件“living:true”的对象的数组。该程序没有使用“if (test(element.living))”，而是只使用“if (test(element))”，它仍然可以正常工作，这让我很困惑。那么为什么程序测试的是“if (test(element))”而不是“if (test(element.living))”呢？

var SCRIPTS = [
  {
    name: "Adlam",
    ranges: [[125184, 125259], [125264, 125274], [125278, 125280]],
    direction: "rtl",
    year: 1987,
    living: true,
    link: "https://en.wikipedia.org/wiki/Fula_alphabets#Adlam_alphabet"
  },
  {
    name: "Caucasian Albanian",
    ranges: [[66864, 66916], [66927, 66928]],
    direction: "ltr",
    year: 420,
    living: false,
    link: "https://en.wikipedia.org/wiki/Caucasian_Albanian_alphabet"
  },
  {
    name: "Ahom",
    ranges: [[71424, 71450], [71453, 71468], [71472, 71488]],
    direction: "ltr",
    year: 1250,
    living: false,
    link: "https://en.wikipedia.org/wiki/Ahom_alphabet"
  },
  {
    name: "Arabic",
    ranges: [[1536, 1541], [1542, 1548],[1568, 1600]],
    direction: "rtl",
    year: 400,
    living: true,
    link: "https://en.wikipedia.org/wiki/Arabic_script"
  },
  {
    name: "Imperial Aramaic",
    ranges: [[67648, 67670], [67671, 67680]],
    direction: "rtl",
    year: 800,
    living: false,
    link: "https://en.wikipedia.org/wiki/Aramaic_alphabet"
  },
  {
    name: "Armenian",
    ranges: [[1329, 1367], [1369, 1376], [1377, 1416],[64275, 64280]],
    direction: "ltr",
    year: 405,
    living: true,
    link: "https://en.wikipedia.org/wiki/Armenian_alphabet"
  },
  {
    name: "Avestan",
    ranges: [[68352, 68406], [68409, 68416]],
    direction: "rtl",
    year: 400,
    living: false,
    link: "https://en.wikipedia.org/wiki/Avestan_alphabet"
  },
  {
    name: "Balinese",
    ranges: [[6912, 6988], [6992, 7037]],
    direction: "ltr",
    year: 1000,
    living: true,
    link: "https://en.wikipedia.org/wiki/Balinese_script"
  },
  {
    name: "Bamum",
    ranges: [[42656, 42744], [92160, 92729]],
    direction: "ltr",
    year: 1896,
    living: true,
    link: "https://en.wikipedia.org/wiki/Bamum_script"
  },
  {
    name: "Bassa Vah",
    ranges: [[92880, 92910], [92912, 92918]],
    direction: "ltr",
    year: 1950,
    living: false,
    link: "https://en.wikipedia.org/wiki/Bassa_alphabet"
  },
  {
    name: "Batak",
    ranges: [[7104, 7156], [7164, 7168]],
    direction: "ltr",
    year: 1300,
    living: true,
    link: "https://en.wikipedia.org/wiki/Batak_alphabet"
  },
  {
    name: "Bengali",
    ranges: [[2432, 2436], [2437, 2445], [2447, 2449], [2451, 2473],[2492, 2501]],
    direction: "ltr",
    year: 1050,
    living: true,
    link: "https://en.wikipedia.org/wiki/Bengali_alphabet"
  }
  ]

function filter(array, test) {
 let passed = [];
 for (let element of array) {
  if (test(element)) {
	passed.push(element);
   }
  }
 return passed;
}
console.log(filter(SCRIPTS, function(element) {return element.living}));

标签： javascript

解决方案

它之所以起作用，是因为在filter,test是这个函数（它接收它作为test参数的值）：

function(element) {return element.living}

...返回living传入元素的属性。

这意味着

if (test(element)) {
    passed.push(element);
}

有效地

if (element.living) {
    passed.push(element);
}

因为test所做的只是返回属性的值。

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