JS judge whether array / object array 1 contains array / object array 2

The problem we often encounter in development is to find out whether an element exists in the array , And the method used in most cases is indexOf(), If the element does not exist, the array will return -1, Otherwise, return the subscript of the element in the array .

But what about object arrays ？ Use it directly indexOf It can't express the result intuitively .

character string ：

Example ：

var str = 'Hello world!';
console.log( str.indexOf('e') ); //  Exists in the string , Return to position  1
console.log( str.indexOf('d') ); //  Exists in the string , Return to position  10
console.log( str.indexOf('x') ); //  Does not exist in string , return  -1

Array ：

Array.indexOf()  Search for elements in the array , And return to where it is , Returns if it does not exist -1;

Array.includes()  Determine whether an array contains a specified value , return true, Otherwise return to false.

Array.find()  Return compliance with incoming test （ function ） Conditional array elements , Otherwise return to  undefined;

Array.findIndex()   Return compliance with incoming test （ function ） Conditional array element index , Otherwise return to  -1;

Array.some()   Check whether any element in the array element meets the specified conditions （ function ）. return  true, Otherwise return to  false;

Example ：

var arr = ['cat', 'dog', 'bat'];

// indexOf()  Method 
console.log( arr.indexOf('cat') ) //  There is   Return to position  0
console.log( arr.indexOf('dog') ) //  There is   Return to position  1
console.log( arr.indexOf('tiger') ) //  non-existent   return  -1

// includes()  Method 
console.log( arr.includes('cat' ) ) //  There is   return  true
console.log( arr.includes('dog' ) ) //  There is   return  true
console.log( arr.includes('tiger') ) //  non-existent   return  false

// find()  Method 
console.log( arr.find(v => v == 'dog' ) ) //  There is   Return value  dog
console.log( arr.find(v => v == 'tiger') ) //  non-existent   return  undefined

// findIndex()  Method 
console.log( arr.findIndex(v => v == 'cat' ) ) //  There is   return  0
console.log( arr.findIndex(v => v == 'dog' ) ) //  There is   return  1
console.log( arr.findIndex(v => v == 'tiger') ) //  non-existent   return  -1

// some()  Method 
console.log( arr.some(v => v == 'cat' ) ) //  There is   return  true
console.log( arr.some(v => v == 'dog' ) ) //  There is   return  true
console.log( arr.some(v => v == 'tiger') ) //  non-existent   return  false

An array of objects ：

Example ：

var arr = [{name:'cat'}, {name:'dog'}, {name:'bat'}];
var arr2 = [{name:'cat'}, {name:'dog'}]

console.log( arr.find(v => v.name == 'dog' ) ) //  There is   return  {name: "dog"}
console.log( arr.find(v => v.name == 'tiger') ) //  non-existent   return  undefined

console.log( arr.findIndex(v => v.name == 'cat' ) ) //  There is   return  0
console.log( arr.findIndex(v => v.name == 'dog' ) ) //  There is   return  1
console.log( arr.findIndex(v => v.name == 'tiger') ) //  non-existent   return  -1

console.log( arr.some(v => v.name == 'cat' ) ) //  There is   return  true
console.log( arr.some(v => v.name == 'dog' ) ) //  There is   return  true
console.log( arr.some(v => v.name == 'tiger') ) //  non-existent   return  false

//  Circular judgement arr And arr2 Whether there are the same elements , Same addition isdelete:false Field , Different addition isdelete:true
this.arr.map((item) => {
  let bool = this.arr2.findIndex((it) => {
    return item.name == it.name
  })
  if (bool !== -1) {
    item.isdelete = false
  } else {
    item.isdelete = true
  }
})