Encapsulation of js methods commonly used during development (summary)

This article will introduce to you the js method encapsulation commonly used during development. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

1. Determine whether it is an array

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

2. Determine whether it is a function (three types)

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

3. Array deduplication, only consider that the elements in the array are numbers or strings

function newarr(arr){
var arrs = [];
for(var i =0;i<arr.length;i++){
if(arrs.indexOf(arr[i])== -1){
arrs.push(arr[i])
}
}
return arrs;
}

4. Dynamic deduplication

var arr = [1,2, 3, 4];
function add() {
var newarr = [];
$('.addEle').click(() => {
var rnd = Math.ceil(Math.random() * 10);
newarr.push(rnd)
for (var i =0; i < newarr.length; i++) {
if (arr.indexOf(newarr[i]) == -1) {
arr.push(newarr[i])
arr.sort(function (a, b) {
return b - a //降序
});
}
}
console.log(arr)//[1,2,3,4,5,6,7,8,9]
})
}
add()

5. Remove string spaces (including three situations)

function trim(str) {
return str.replace(/^[" "||"　"]*/,"").replace(/[" "|"　"]*$/,"");// 去除头和尾
return str.replace(/\s/g,'');//去除所有空格
return str.replace(/(\s*$)/g,"");//去除右边所有空格
}

6. Determine whether it is an email address

function isEmail(emailStr) {
var reg = /^[a-zA-Z0-9]+([._-]*[a-zA-Z0-9]*)*@[a-zA-Z0-9]+.[a-zA-Z0-9{2,5}$]/;
var result = reg.test(emailStr);
if (result) {
alert("ok");
} else {
alert("error");
}
}

7. Determine whether it is an email address Mobile phone number

function isMobilePhone(phone) {
var reg = /^1\d{10}$/;
if (reg.test(phone)) {
alert('ok');
} else {
alert('error');
}
}

8. Get the number of the first element in an object

function getObjectLength(obj){
var i=0;
for( var attrin obj){
if(obj.hasOwnProperty(attr)){
i++;
}
}
console.log(i);
}
var obj = {name:'kob',age:20};
getObjectLength(obj) //2

9. Get the number of elements relative to the browser window Position, returns an {x,y} object

function getPosition(element) {
var offsety = 0;
offsety += element.offsetTop;
var offsetx = 0;
offsetx += element.offsetLeft;
if (element.offsetParent != null) {
getPosition(element.offsetParent);
}
return { Left: offsetx, Top: offsety };
}　

10. Determine the number of times a certain letter appears in the string

var str = 'To be, or not to be, that is the question.';
var count = 0;
var pos = str.indexOf('e');
while (pos !== -1) {
count++;
pos = str.indexOf('e', pos + 1);
}
console.log(count) //4

11 , Calculate the element with the most occurrences in the array

var arrayObj = [1,1, 2, 3, 3, 3,4, 5, 5];
var tepm = '',count =0;
var newarr = new Array();
for(var i=0;i<arrayObj.length;i++){
if (arrayObj[i] != -1) {
temp = arrayObj[i];
}
for(var j=0;j<arrayObj.length;j++){
if (temp == arrayObj[j]) {
count++;
arrayObj[j] = -1;
}
}
newarr.push(temp + ":" + count);
count = 0;
}
for(var i=0;i<newarr.length;i++){
　　console.log(newarr[i]);
}

12. Array filter (search function)

var fruits = ['apple','banana', 'grapes','mango', 'orange'];
function filterItems(query) {
return fruits.filter(function(el) {
return el.toLowerCase().indexOf(query.toLowerCase()) > -1;
})
}

console.log(filterItems('ap')); // ['apple', 'grapes']

13. Copy object (No. A)

//第一种
var cloneObj =function(obj) {
var newObj = {};
if (obj instanceof Array) {
newObj = [];
}
for (var keyin obj) {
var val = obj[key];
newObj[key] = typeof val === 'object' ? cloneObj(val) : val;
}
return newObj;
};
//第二种
function clone(origin , target){
var target = target || {};
for(var propin origin){
target[prop] = origin[prop];
}
return target;
}　

14. Deep cloning

var newObj ={};
function deepClone(origin,target){
var target = target || {},
toStr = Object.prototype.toString,
arrStr = "[object Array]";

for(var propin origin){
if(origin.hasOwnProperty(prop)){
if(origin[prop] != "null" && typeof(origin[prop]) == 'object'){//判断原型链
target[prop] = (toStr.call(origin[prop]) == arrStr) ? [] : {}//判断obj的key是否是数组
deepClone(origin[prop],target[prop]);//递归的方式
}else{
target[prop] = origin[prop];
}
}
}
return target

}

deepClone(obj,newObj);
console.log(newObj)

15. Find the maximum and minimum value of the array

Array.prototype.max = function(){
return Math.max.apply({},this)
}
 
Array.prototype.min = function(){
return Math.min.apply({},this)
}
 
console.log([1,5,2].max())

16. JSON array deduplication

function UniquePay(paylist){
var payArr = [paylist[0]];
for(var i =1; i < paylist.length; i++){
var payItem = paylist[i];
var repeat = false;
for (var j =0; j < payArr.length; j++) {
if (payItem.name == payArr[j].name) {
repeat = true;
break;
}
}
if (!repeat) {
payArr.push(payItem);
}
}
return payArr;
}　

17. Compare two arrays and take out the intersection

Array.intersect = function () {
var result = new Array();
var obj = {};
for (var i =0; i < arguments.length; i++) {
for (var j =0; j < arguments[i].length; j++) {
var str = arguments[i][j];
if (!obj[str]) {
obj[str] = 1;
}
else {
obj[str]++;
if (obj[str] == arguments.length)
{
result.push(str);
}
}//end else
}//end for j
}//end for i
return result;
}
console.log(Array.intersect(["1","2", "3"], ["2","3", "4", "5", "6"]))

18. Array sum Object comparison. Remove the object whose key is the same as the array element

var arr = ['F00006','F00007','F00008'];
var obj = {'F00006':[{'id':21}],'F00007':[{'id':11}]}
var newobj = {};
for(var itemin obj){
if(arr.includes(item)){
newobj[item] = obj[item]
}
}
console.log(newObj)

19. Delete an element in the array

//第一种
Array.prototype.remove = function(val){
var index = this.indexOf(val);
if(index !=0){
this.splice(index,1)
}
}
[1,3,4].remove(3)
//第二种
function remove(arr, indx) {
for (var i =0; i < arr.length; i++) {
var index = arr.indexOf(arr[i]);
if (indx == index) {
arr.splice(index, 1)
}
}
return arr
}

20. Determine whether the array contains an element Element

Array.prototype.contains = function (val) {
for (var i =0; i < this.length; i++) {
if (this[i] == val) {
return true;
}
}
return false;
};

[1, 2,3, 4].contains(2)//true

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