Js array Notes

This is the second day of my participation in the August Text Challenge.More challenges in August

Js array Notes

Implements the summation of identical elements in an object

    const obj = {
        "total_mobile": {
            "user_cnt_connect": 1."user_cnt_fail": 1."cnt_fail": 1."fail_user_ratio": 1.87."cnt_fail_per_user": 1."fail_ratio": 1
        },
        "total_unicom": {
            "user_cnt_connect": 2."user_cnt_fail": 2."cnt_fail": 2."fail_user_ratio": 2."cnt_fail_per_user": 2."fail_ratio": 2.28
        },
        "total_chinanet": {
            "user_cnt_connect": 3."user_cnt_fail": 1.89."cnt_fail": 3."fail_user_ratio": 1."cnt_fail_per_user": 1."fail_ratio": 1}}const {
        total_mobile,
        total_chinanet,
        total_unicom
    } = obj;
    const total_mobile_chinanet = {}; / / move | telecom
    const total_mobile_unicom = {}; / / move | unicom
    const total_unicom_chinanet = {}; / / unicom | telecom
    for (let k in total_mobile) {
        total_mobile_chinanet[k] = total_mobile[k] + total_chinanet[k];
        total_mobile_unicom[k] = total_mobile[k] + total_unicom[k];
        total_unicom_chinanet[k] = total_chinanet[k] + total_unicom[k];
    }
    console.log(total_mobile_chinanet)
    console.log(total_mobile_unicom)
    console.log(total_unicom_chinanet)
    var num = 2.446242342;
    num = num.toFixed(2);
    console.log(num); / / 2.45
    console.log(typeof num); // string
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1. Js iterates through the array and adds new attributes to each object element

 let arry = this.teamList
 let arryNew = []
 arry.map((item, index) = > {
     arryNew.push(Object.assign({}, item, {
         disabled: true}})))Copy the code

2. Js delete an item from array splice()

var id = '3'
var tagList = [{
        "parentTagId": "1"."parentTagName": "School"."childTagId": "3"."childTagName": "High school"
    },
    {
        "parentTagId": "1"."parentTagName": "School"."childTagId": "4"."childTagName": "Junior"}]for (var i = 0; i < tagList.length; i++) {
    if (tagList[i].childTagId === id) {
        tagList.splice(i, 1); }}console.log(JSON.stringify(tagList))
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3. Js randomly generates a four-digit verification code (including letters and numbers)

 function checkCodeofRandom() {
     // An array of randomly selected samples is required
     var nums = new Array("q"."w"."e"."r"."t"."y"."u"."i"."o"."p"."a"."s"."d"."f"."g"."h"."j"."k"."l"."z"."x"."c"."v"."b"."n"."m"."A"."W"."E"."R"."T"."Y"."U"."I"."O"."P"."A"."S"."D"."F"."G"."H"."J"."K"."L"."Z"."X"."C"."V"."B"."N"."M"."0"."1"."2"."3"."4"."5"."6"."Seven"."8"."9");
     // Initializes the concatenation string
     var str = "";
     for (i = 0; i < 4; i++) {
         // Generate a number between 0 and 61 each time as a random subscript to obtain the captcha
         var p = Math.floor(Math.random() * 1000) % 62;
         // Splicing the verification code randomly selects uppercase and lowercase letters and numbers
         str += nums[p];
     }
     console.log(str)
     return str;
 }
 checkCodeofRandom()

 // No server verification is required
 // The client checks whether the verification code entered by the user is consistent with the randomly generated verification code
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3. Object splicing.

Put the data of two objects in one object

Methods a

var tmpa = {
    q: 'qq'.w: 'ww'
}
var tmpb = {
    e: 'ee'.r: 'rr'
}
var tmp = Object.assign(tmpa, tmpb)
console.log("tmp", tmp)
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Method 2

var tmpa = {
    q: 'qq'.w: 'ww'
}
vartmpb = { ... tmpa,e: 'ee'.r: 'rr'
}
console.log("tmp", tmpb)
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4. A deep copy

function deepCopy(obj) {
    if (typeofobj ! = ='object') {
        return
    }
    const str = JSON.stringify(obj)
    return JSON.parse(str)
}

export default deepCopy
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5. Picture placeholder hidden

img:not([src]):not([srcset]) {
    visibility: hidden;
}
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6. Replace the letters after the specified string

var abc = 'adadada=ss';
var j = abc.substring(abc.indexOf('=') + 1, abc.length);
var dsd = abc.replace(j, 'haha');
dsd = 'adadada=haha'
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7. How do I set the value of val to be null for traversing multiple objects

let obj = {
    "a": 1."b": 2
};
Object.keys(obj).map(key= > obj[key] = ' ')
console.log(obj)
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8. Array deduplication

 function unique(arr) {
     return arr.filter(function(item, index, arr) {
         // Current element, the first index in the original array == current index value, otherwise return current element
         return arr.indexOf(item, 0) === index;
     });
 }
 var arr = [1.1.'true'.'true'.true.true.15.15.false.false.undefined.undefined.null.null.NaN.NaN.'NaN'.0.0.'a'.'a', {}, {}];
 console.log(unique(arr)) //[1,"true",true,15,false,null,null,"NaN",0,"a",{},{}]
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