javascript 中关于array的常用方法详解

/** * 去重操作,有序状态 * @param target * @returns {Array} */function unique(target) {  let result = [];  loop: for (let i = 0,n = target.length;i < n; i++) {    for (let x = i + 1;x < n;x++) {      if (target[x] === target[i]) {        continue loop;      }    }    result.push(target[i]);  }  return result;}/** * 去重操作，无序状态，效率最高 * @param target * @returns {Array} */function unique1(target) {  let obj = {};  for (let i = 0,n = target.length; i < n;i++) {    obj[target[i]] = true;  }  return Object.keys(obj);}/** * ES6写法,有序状态 * @param target * @returns {Array} */function unique2(target) {  return Array.from(new Set(target));}function unique3(target) {  return [...new Set(target)];}

/** * 返回数组中的最小值，用于数字数组 * @param target * @returns {*} */function min(target) {  return Math.min.apply(0,target);}/** * 返回数组中的最大值，用于数字数组 * @param target * @returns {*} */function max(target) {  return Math.max.apply(0,target);}/** * 从数组中随机抽选一个元素出来 * @param target * @returns {*} */function random(target) {  return target[Math.floor(Math.random() * target.length)];}

/** * 移除数组中指定位置的元素，返回布尔表示成功与否 * @param target * @param index * @returns {boolean} */function removeAt(target,index) {  return !!target.splice(index,1).length;}/** * 移除数组中第一个匹配传参的那个元素，返回布尔表示成功与否 * @param target * @param item * @returns {boolean} */function remove(target,item) {  const index = target.indexOf(item);  if (~index) {    return removeAt(target,index);  }  return false;}/** * 对数组进行洗牌 * @param array * @returns {array} */function shuffle(array) {  let m = array.length, t, i;  // While there remain elements to shuffle…  while (m) {    // Pick a remaining element…    i = Math.floor(Math.random() * m--);    // And swap it with the current element.    t = array[m];    array[m] = array[i];    array[i] = t;  }  return array;}/** * 对数组进行平坦化处理，返回一个一维的新数组 * @param target * @returns {Array} */function flatten (target) {  let result = [];  target.forEach(function(item) {    if(Array.isArray(item)) {      result = result.concat(flatten(item));    } else {      result.push(item);    }  });  return result;}/** * 过滤属性中的null和undefined,但不影响原数组 * @param target * @returns {Array.<T>|*} */function compat(target) {  return target.filter(function(el) {    return el != null;  })}

/** * 根据指定条件（如回调或对象的某个属性）进行分组，构成对象返回。 * @param target * @param val * @returns {{}} */function groupBy(target,val) {  var result = {};  var iterator = isFunction(val) ? val : function(obj) {    return obj[val];  };  target.forEach(function(value,index) {    var key = iterator(value,index);    (result[key] || (result[key] = [])).push(value);  });  return result;}function isFunction(obj){  return Object.prototype.toString.call(obj) === '[object Function]';}// 例子function iterator(value) {  if (value > 10) {    return 'a';  } else if (value > 5) {    return 'b';  }  return 'c';}var target = [6,2,3,4,5,65,7,6,8,7,65,4,34,7,8];console.log(groupBy(target,iterator));/** * 获取对象数组的每个元素的指定属性，组成数组返回 * @param target * @param name * @returns {Array} */function pluck(target,name) {  let result = [],prop;  target.forEach(function(item) {    prop = item[name];    if (prop != null) {      result.push(prop);    }  });  return result;}/** * 根据指定条件进行排序，通常用于对象数组 * @param target * @param fn * @param scope * @returns {Array} */function sortBy(target,fn,scope) {  let array = target.map(function(item,index) {    return {      el: item,      re: fn.call(scope,item,index)    };  }).sort(function(left,right) {    let a = left.re, b = right.re;    return a < b ? -1 : a > b ? 1 : 0;  });  return pluck(array,'el');}

/** * 对两个数组取并集 * @param target * @param array * @returns {Array} */function union(target,array) {  return unique(target.concat(array));}/** * ES6的并集 * @param target * @param array * @returns {Array} */function union1(target,array) {  return Array.from(new Set([...target,...array]));}/** * 对两个数组取交集 * @param target * @param array * @returns {Array.<T>|*} */function intersect(target,array) {  return target.filter(function(n) {    return ~array.indexOf(n);  })}/** * ES6 交集 * @param target * @param array * @returns {Array} */function intersect1(target,array) {  array = new Set(array);  return Array.from(new Set([...target].filter(value => array.has(value))));}/** * 差集 * @param target * @param array * @returns {ArrayBuffer|Blob|Array.<T>|string} */function diff(target,array) {  var result = target.slice();  for (var i = 0;i < result.length;i++) {    for (var j = 0; j < array.length;j++) {      if (result[i] === array[j]) {        result.splice(i,1);        i--;        break;      }    }  }  return result;}/** * ES6 差集 * @param target * @param array * @returns {Array} */function diff1(target,array) {  array = new Set(array);  return Array.from(new Set([...target].filter(value => !array.has(value))));}

/** * 判定数组是否包含指定目标 * @param target * @param item * @returns {boolean} */function contains(target,item) {  return target.indexOf(item) > -1;}

const _slice = Array.prototype.slice;Array.prototype.pop = function() {  return this.splice(this.length - 1,1)[0];};Array.prototype.push = function() {  this.splice.apply(this,[this.length,0].concat(_slice.call(arguments)));  return this.length;};Array.prototype.shift = function() {  return this.splice(0,1)[0];};Array.prototype.unshift = function() {  this.splice.apply(this,    [0,0].concat(_slice.call(arguments)));  return this.length;};