用属性过滤两个json数组

Question

i have to filter first array if the same object is present in second array using type script/ javascript

here is my arrays

var students = [{id: 1, name : 'SSS'},
{id: 2, name : 'SSa'},
{id: 3, name : 'SSb'},
{id: 4, name : 'SSc'},
{id: 5, name : 'SSd'}];

var emp = [{id: 1, name : 'SSS'},
{id: 4, name : 'SSc'},
{id: 5, name : 'SSd'}];

Output should be

var finalarr = [{id: 2, name : 'SSa'},
{id: 3, name : 'SSb'}]

i have tried below but produces wrong ouputs

for (let i = 0; i < students.length; i++) {
    for (let j = 0; j < emp.length; j++) {
    if (students[i].id != emp[j].id) {
    finalarr.push(students[i]);
    }
}
}
console.log(finalarr);

// below is my actual application code

this.appointmentTypes.filter((data, index) => this.typesData.includes(this.typesData[index].appointmentType.id))

Answer 1

Objects are references to memory locations - they'll never === each other unless they reference the same memory location, so includes won't work. Iterate over the whole array and test the names and IDs instead:

 var students=[{id:1,name:'SSS'},{id:2,name:'SSa'},{id:3,name:'SSb'},{id:4,name:'SSc'},{id:5,name:'SSd'}] var emp=[{id:1,name:'SSS'},{id:4,name:'SSc'},{id:5,name:'SSd'}] const finalArr = students.filter(({ id, name }) => !emp.some(exclude => exclude.id === id && exclude.name === name) ); console.log(finalArr); 

Answer 2

Your imperative attempt w/ loops fails because you push to final array when finding the first item with a different id.

It should be like

 var students = [{id: 1, name : 'SSS'}, {id: 2, name : 'SSa'}, {id: 3, name : 'SSb'}, {id: 4, name : 'SSc'}, {id: 5, name : 'SSd'}]; var emp = [{id: 1, name : 'SSS'}, {id: 4, name : 'SSc'}, {id: 5, name : 'SSd'}]; var finalarr = [] for (let i = 0; i < students.length; i++) { let found = false // flag for (let j = 0; j < emp.length && !found; j++) { found = students[i].id === emp[j].id } if (!found) finalarr.push(students[i]) } console.log(finalarr) 

But a better option would be to create a Set of ids from the second array. new Set(emp.map(item => item.id)) And the simply filter out all elements of the first array which ids are in the set using filter(item => !set.has(item.id))

 var students = [{id: 1, name : 'SSS'}, {id: 2, name : 'SSa'}, {id: 3, name : 'SSb'}, {id: 4, name : 'SSc'}, {id: 5, name : 'SSd'}]; var emp = [{id: 1, name : 'SSS'}, {id: 4, name : 'SSc'}, {id: 5, name : 'SSd'}]; console.log( students.filter( (set => item => !set.has(item.id))(new Set(emp.map(item => item.id))) ) ) 

Answer 3

Set and Map tend to be great for solving filtration problems.

See below for more info 👇

 // Input. const students = [{id: 1, name : 'SSS'},{id: 2, name : 'SSa'},{id: 3, name : 'SSb'},{id: 4, name : 'SSc'},{id: 5, name : 'SSd'}] const emp = [{id: 1, name : 'SSS'},{id: 4, name : 'SSc'},{id: 5, name : 'SSd'}] // Filter. const filter = (A, B) => { const set = new Set(B.map(JSON.stringify)) return A.filter(x => !set.has(JSON.stringify(x))) } // Output. const output = filter(students, emp) // Proof. console.log(output)