使用计算的属性键访问对象值答案

【问题标题】：Access object value with computed property keys使用计算的属性键访问对象值
【发布时间】：2017-10-19 10:45:23
【问题描述】：

我正在编写一个小助手，它应该获取数组的最小项。

该函数将Array 作为第一个参数和访问对象属性“rest”参数的“路径”。

例如：minItem(stops, 'duration', 'total');

console.log：// [object object][duration][total]

预期：// Number, Which is the value of total

const stops = 
[{"transport":"train","departure":"Paris","arrival":"Madrid","duration":
{"h":"03","m":"15","total":195},"cost":160,"discount":0,
"reference":"TPM0315","initialPrice":160},
{"transport":"bus","departure":"Paris","arrival":"Madrid",
"duration":{"h":"06","m":"45","total":405},"cost":30,"discount":25,
"reference":"BPM0645","initialPrice":40},
{"transport":"car","departure":"Paris","arrival":"Madrid","duration":
{"h":"05","m":"45","total":345},"cost":120,"discount":0,
"reference":"CPM0545","initialPrice":120}];


/** @function minItem */
const minItem = (array, ...args) => {
  const keys = `['${[...args].join('\'][\'')}']`;
  array.reduce((a, b) => {
    console.log(b + keys);
    return a + keys <= b + keys ? a : b;
  }, {});
};

minItem(stops, 'duration', 'total');

【问题讨论】：

标签： javascript object ecmascript-6

【解决方案1】：

在使用Array#map 创建的最小值数组上使用Math#min 获取最小值。要获取args 路径的值，可以使用Array#reduce 迭代键：

const stops = [{"transport":"train","departure":"Paris","arrival":"Madrid","duration":{"h":"03","m":"15","total":195},"cost":160,"discount":0,"reference":"TPM0315","initialPrice":160},{"transport":"bus","departure":"Paris","arrival":"Madrid","duration":{"h":"06","m":"45","total":405},"cost":30,"discount":25,"reference":"BPM0645","initialPrice":40},{"transport":"car","departure":"Paris","arrival":"Madrid","duration":{"h":"05","m":"45","total":345},"cost":120,"discount":0,"reference":"CPM0545","initialPrice":120}];


/** @function minItem */
const getPathValue = (src, path) => path.reduce((p, k) => typeof p === 'object' ? p[k] : p, src);

const minItem = (array, ...args) => Math.min(...array.map((o) => getPathValue(o, args)));

console.log(minItem(stops, 'duration', 'total'));

【讨论】：