如何检查对象数组中是否存在id值

Question

Given an array "posts" of objects {id: "x", title: "title"}, i need to verify whether there is a previously entered id before entering a new post (via form in which id is a field).

I tried looping through posts, but it causes problems on entering repeated new data. Thank you for your help, this is driving me mad.

// ADD NEW POST FROM FORM TO ARRAY
$("#form").submit(function(event) {
    event.preventDefault();
    var id = Number($("#idPost").val());
    var title = $("#titlePost").val();
    var date = new Date($("#data").val());
// CHECK IF id ALREADY EXISTS, IF YES, BLOCK ENTRY    
    for(num of posts){
        console.log (id, num.id);
        if(id === num.id){ 
            console.log("error");
        } else {
            var post = new Post(id, title, date);
        }                
    };      
});

Answer 1

As @Andreas suggested, you can use Array.Some() to find element exist in array or not.

 var found = posts.some(el => el.id  === id ); // It returns true if id exist in an array
 if(found)
 {
  //Your codes here
 }

Or you can try with Array.Filter() to find element is exist or not in array.

var found = posts.filter(el => el.id === id).length > 0; // .length returns 1 if id exist in an array
if(found)
{
   //Your code goes here
}

You can try Array.find() or Array.IndexOf() to perform same operation

Following implementation with Array.Some()

 //Lets consider below is the value in posts arry var posts = [ { id: 1, username: 'foo' },{ id: 2, username: 'bar' } ]; var newObj = {"id": 3, "username": 'prasad'}; //console.log(posts); var found = posts.some(el => el.id === 2 ); if(found) { for(num of posts){ //console.log (3, num.id); if(4 === num.id){ //Your code //console.log("error"); } else { //Your code //console.log(num); } }; posts.push(newObj); console.log(posts); } 

Answer 2

You can use either Array.prototype.some() as Andreas suggested or use Array​.prototype​.find() .

Array.prototype.some() will just return true or false and will not return the matching object. If you need the object, use find() as follows:

$("#form").submit(function(event) {
event.preventDefault();
var id = Number($("#idPost").val());
var title = $("#titlePost").val();
var date = new Date($("#data").val());
var objectPresent = posts.find(function(post) {
   return post.id === id;
});
if(!objectPresent) {
   var post = new Post(id, title, date);
} else {
  console.log(objectPresent.id,"is already taken up by ", objectPresent.title);
}

});

Answer 3

I think you should use the JSON object, it will help you to identify easily, that how to identify, is key present in JSON object list or not

JSON_Object.hasOwnProperty(ID)

---

var x = {};
x[1] = "{'title1':'title1'}";
x[2] = "{'title2':'title2'}";
x[3] = "{'title3':'title3'}";

if(x.hasOwnProperty(1)){
 console.log('value present');
}

if(x.hasOwnProperty(5)){
 console.log('value not present');
}

This may help you.

This is just a way to resolve your problem. Use this, thanks me later, cheers :)

Answer 4

This should work:

if (postExists(posts, id)){
    // invlaid post entry
} else {
    // add new post
}

function postExists(posts, id) {
    return posts.some(function(post){
        return post.id == id;
    });
}