How to access the properties and methods of objects in js? (code example)

The content of this article is to introduce how js accesses the properties and methods of objects? (code example). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

The properties and methods of an object are collectively called members of the object.

Accessing the properties of an object

In JavaScript, you can use "." and "[] ” to access the properties of the object.

The difference between the two: "." notation is generally used as a static object to access properties. The "[ ]" notation is very useful when accessing attributes dynamically.

var object = {name:'xiaoming',age:29};
var name1 = object.name;var name2 = object['name'];

Methods to access objects

In JavaScript, you can only use "." to access methods of objects .

function Person(){
    this.name = 'xiaoming';
    this.age = 29;
    this.say = function(){
        alert('This is person');
    }          
}
var student = new Person();
alert(student.name);
alert(student['age']);
student.say();  //使用" . "访问对象方法

Two questions derived from:

1. Determine the number of occurrences in a string The most characters, count the number

var str = 'Thisthebesttimesewerty';
var obj = {};
for(var i=0; i<str.length;i++){
    var char = str[i];
 // var char = str.charAt(i); //charAt()可返回指定位置的字符，i为字符的下标，从0开始
    if(obj[char]){
        obj[char]++; //char是obj对象的一个属性，如果存在次数加1
    }else{
        obj[char] = 1; //如果不存在，保存在obj中并计数为1
    }
}

var max = 0;
var maxChar = null;
for(var key in obj){
    if(max < obj[key]){
        max = obj[key]; //出现最多次数max
        maxChar = key;  //出现次数最多的字符maxChar
    }
}

2. Write the arraysSimilar function to determine whether the two incoming arrays are similar.

Specific requirements:

1. The members in the array have the same type, but the order can be different. For example, [1, true] is similar to [false, 2].

2. The length of the arrays is the same.

3. The type judgment range needs to be distinguished: String, Boolean, Number, undefined, null, function, date, window.

When all the above are satisfied, "Judgment Result: Pass" is returned, otherwise "Judgment Result: Fail" is returned.

function arraysSimilar(arr1,arr2){
    if(!(arr1 instanceof Array) || !(arr2 instanceof Array)){
         return false;
    }   
    if(arr1.length !== arr2.length){
         return false;
    }

    var i=0, n=arr1.length, countMap1={}, countMap2 = {}, t1, t2,
    TYPES = ['string','boolean','number','undefined','null','function','date','window'];

    for(i; i<n; i++){
         t1 = typeOf(arr1[i]);
         t2 = typeOf(arr2[i]);
         if(countMap1[t1]){
             countMap1[t1]++;
         }  else{
             countMap1[t1] = 1;
         }

        if(countMap2[t2]){
             countMap2[t2]++;
         }  else{
             countMap2[t2] = 1;
         }
    }
 
    for(i=0; i<TYPES.length; i++){
        if(countMap1[TYPES[i]] != countMap2[TYPES[i]]){
            return false;
        }
    }
    return true;
}

function typeOf(ele){
    var r;
    if(ele === null){
        r = 'null';
    }
    else if(ele === 'window'){
        r = 'window';
    }
    else if(ele instanceof Array){
        r  = 'array';
    }
    else if(ele instanceof Date){
        r = 'date';
    }
    else{
        r = typeof(ele);
    }
    return r;
}

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