统计匹配检索规则的物品数量

题目

给你一个数组 items ，其中 items[i] = [typei, colori, namei] ，描述第 i 件物品的类型、颜色以及名称。

另给你一条由两个字符串 ruleKey 和 ruleValue 表示的检索规则。

如果第 i 件物品能满足下述条件之一，则认为该物品与给定的检索规则 匹配 ：

ruleKey == "type" 且 ruleValue == typei 。 ruleKey == "color" 且 ruleValue == colori 。 ruleKey == "name" 且 ruleValue == namei 。 统计并返回 匹配检索规则的物品数量 。

示例 1：
输入：items = [["phone","blue","pixel"],["computer","silver","lenovo"],["phone","gold","iphone"]], ruleKey = "color", ruleValue = "silver"
输出：1
解释：只有一件物品匹配检索规则，这件物品是 ["computer","silver","lenovo"] 。

示例 2：
输入：items = [["phone","blue","pixel"],["computer","silver","phone"],["phone","gold","iphone"]], ruleKey = "type", ruleValue = "phone"
输出：2
解释：只有两件物品匹配检索规则，这两件物品分别是 ["phone","blue","pixel"] 和 ["phone","gold","iphone"] 。注意，["computer","silver","phone"] 未匹配检索规则。
 

提示：
1 <= items.length <= 104
1 <= typei.length, colori.length, namei.length, ruleValue.length <= 10
ruleKey 等于 "type"、"color" 或 "name"
所有字符串仅由小写字母组成

题解

定义一个map，用于定位ruleKey所在的索引； 循环二维数组，查找二维数组的每个元素(一位数组)[ruleKey所在的索引] 是否等于ruleValue;

var countMatches = function(items, ruleKey, ruleValue) {
    let num = 0;
    let map = new Map();
    map = {
        type : 0,
        color: 1,
        name: 2
    }

    const index = map[ruleKey];
    items.forEach((eles) => {
        if (eles[index] === ruleValue) {
            num++;
        }
    })
    return num;
};

或者：

根据题意item 是由 [type, color, name]组成的二维数组， 通过map定义三个属性的下标{type: 0,color: 1,name: 2 }并根据ruleKey动态取出来，剩下的一个 filter 就搞定了

/**
 * @param {string[][]} items
 * @param {string} ruleKey
 * @param {string} ruleValue
 * @return {number}
 */
var countMatches = function(items, ruleKey, ruleValue) {
    return items.filter(item =>item[{type: 0,color: 1,name: 2 }[ruleKey]] === ruleValue).length
};