JS 数组对象去重排序等一些常用方法整理

1、数组对象去重

1. 数组去重，数组中元素为数字或者字符串

1. 单个数组去重

//1.
function unique(arr) {
   return [...new Set(arr)] 
}
//2.
function unique(arr) {
    return Array.from(new Set(arr))
}
//3.
function unique(arr) {
    var arrs = [];
    for (var i = 0; i < arr.length; i++) {
        if (arrs.indexOf(arr[i]) == -1) {
            arrs.push(arr[i])
        }
    }
    return arrs;
}

2. 两个数组合并去重

//1.
function unique(arr1, arr2) {  
 return Array.from(new Set([...arr1, ...arr2]))  
}
//2.
function unique(a, b) {
    let arr = a.concat(b)
    arr = arr.sort(function (a, b) {
        return a - b;
    });
    let result = [arr[0]]
    for (let i = 1, len = arr.length; i < len; i++) {
        arr[i] !== arr[i - 1] && result.push(arr[i])
    }
    return result
}

2. 数组对象去重，数组中元素为对象，去除相同 key 值的对象

//1. 
function unique(arr, keyName) {
    let obj = {};
    return arr.reduce((cur, next) => {
        obj[next[keyName]] ? "" : obj[next[keyName]] = true && cur.push(next);
        return cur;
    }, [])
}
//2.
function unique(oldArr,keyName) {
    var allArr = [];
    for (var i = 0; i < oldArr.length; i++) {
        var flag = true;
        for (var j = 0; j < allArr.length; j++) {
            if (oldArr[i][keyName] == allArr[j][keyName]) {
                flag = false;
            };
        };
        if (flag) {
            allArr.push(oldArr[i]);
        };
    };
    return allArr
}

2、判断各种数据类型及无效值

1. 判断是否是一个数组

function isArray(arr){
	return Object.prototype.toString.call(arr) ==='[object Array]';
	//return arr.constructor === Array;
}
isArray([1,2,3]) //true

2. 判断是否是一个函数

function isFunction(fn) {
	return Object.prototype.toString.call(fn) ==='[object Function]';
	//return fn.constructor === Function;
	//return fn instanceof Function;
	//return typeof fn === "function";
}

3. 判断是否是一个字符串

function isString(str) {
	retrun Object.prototype.toString.call(str) ==='[object String]';
	//return str.constructor === String;
	//return typeof str === "string";
}

4. 判断是否是一个对象

function isObject(obj) {
	retrun Object.prototype.toString.call(obj) ==='[object Object]';
	//return obj.constructor === Object;
	//return obj instanceof Object;
	//return typeof obj === "object";
}

5. 判断是否是一个数字

function isNumber(num) {
	retrun Object.prototype.toString.call(num) ==='[object Number]';
	//return num.constructor === Number;
	//return typeof num=== "number";
}

6. 判断是否是一个时间对象

function isDate(date) {
	retrun Object.prototype.toString.call(date) === "[object Date]";
	//return date.constructor === Date;
}

7. 判断是否是一个布尔值

function isBoolean(bool) {
	retrun Object.prototype.toString.call(bool) ==='[object Boolean]';
	//return bool.constructor === Boolean;
	//return typeof bool=== "boolean";
}

8. 判断是否是一个空、无效的值（null、undefined、""、[]、{}、NaN）

function isVoid(obj) {
    if (obj == null || obj == undefined || obj == "") {
        return true
    } else if (Object.prototype.toString.call(obj) === '[object Array]' && obj.length === 0) {
       return true
    } else if (Object.prototype.toString.call(obj) === '[object Object]' && Object.keys(obj).length === 0) {
        return true
    }else if(isNaN(obj)){
        return true
    }
    return false
}