手写lodash.get

1.简单版

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/**  * @param {object} source  * @param {string | string[]} path  * @param {any} [defaultValue]  * @return {any}  */ function get(source, path, defaultValue = undefined) { 　if(typeof object !== 'object') { 　　return defaultValue 　}  if(Array.isArray(path) && !path.length) {     return defaultValue   }   if(typeof path === "string" && !path.trim().length) {     return defaultValue   }   const paths = Array.isArray(path) ? path : path.replace(/\[/g, '.').replace(/\]/g, '').split('.');   return paths.reduce((cur, pre) => (cur || {})[pre], source) || defaultValue; }

　　

　　

　　

2.完整版

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function isDef(target) {   return target !== undefined && target !== null; }   function nextSplit(key) {   const cartfulIndexs = [];   const regx = /\[(\d+)\]/g;   let wholeKey = key;   let matchResult;   while ((matchResult = regx.exec(key))) {     cartfulIndexs.push(matchResult[1]);   }   if (cartfulIndexs.length) {     wholeKey = wholeKey.substring(0, wholeKey.indexOf(cartfulIndexs[0]) - 1);   }   return [wholeKey, ...cartfulIndexs]; }   export function get(target, keyStrs, defaultValue) {   if (!isDef(target)) return defaultValue;     const keyParts = keyStrs     .split(".")     .map(nextSplit)     .flat();     let value = target;     for (let index = 0; index < keyParts.length; index++) {     const key = keyParts[index];     // console.log(key, value);     if (isDef(value[key])) {       value = value[key];     } else {       return defaultValue;     }   }   return value; }