3 functions of toString method in js

1. Three functions of toString method

1. Return a string representing an object

2. Type of detection object

Object.prototype.toString.call(arr) == = "[object Array]"

3. Return the string corresponding to the number.

console.log(10.toString(2)) //10 is specifically for binary '1010'

js contains binary, octal, decimal and octal bases.

2. Return a string representing an object

Object.prototype.toString()

1. toString is a method on the Object prototype.

Every object has a toString() method. By default, toString()方is inherited by every object. If toString is not overridden by the object defined. toString returns '[object type]' where type is the type of the object. The value of type can be Object.

Code:

class Person{
  constructor(name,age){
    this.name=name
    this.age=age
  }
}
let zs=new Person('张三',18)
console.log( zs.toString() ) // [object Object]

• Through the above output statement, we can be sure.
• What is returned is indeed a string representing an object.

3. Custom toString()

We can also define a method to override the default toString method.

A custom toString() method cannot take any arguments and must return a string. The defined toString can return any value we need. If it can carry any information about the object, it will become very useful.

The code is as follows:

class Person{
  constructor(name,age){
    this.name=name
    this.age=age
  }
  // Override Object.prototype.toString()
  toString(){
    return `Person{name=${this.name},age=${this.age}}`
  }
}
let zs=new Person('张三',18)
console.log( zs.toString() ) //Person{name=张三,age=18}

Many built-in objects in JavaScript have rewritten this function to implement functions that are more suitable for their own needs.

• 1. Convert each element of Array to a string and concatenate them one by one, using commas as separators between two elements.
• 2. Boolean If the Boolean value is true, it returns "true". Otherwise returns "false"".
• 3. Date returns the text representation of a date.

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