检查对象值数组是否在另一个数组中但长度不同

Question

I have 2 array of object, just want to check b exist in a, if yes add a new property. but the length of b is dynamic. I will got error of undefined of b.

var a = [{name:'john'},{name:'james'},{name:'jordan'},{name:'joe'}];
var b = [{name:'john'},{name:'joe'}];

var exist = 0;
var c = _.map(a,function(result,i){
    exist = b[i].name.indexOf(a.name) > -1 ? exist = 1 : exist = 0;

    return _.extend({},c,{'exist':exist});
});

any clue?

Answer 1

I would iterate over b objects and for each of them check if they exists in A, like in the following example.

  var a = [ { _id: '5815adb4badf3f311a2cd25b', username: 'david&jane' }, { _id: '5815e40e136c8e33b65b3478', username: 'david+jane' } ]; var b = [ { username: 'david&jane' }, { username: 'david<3jane' }, { username: 'david+jane' }, { username: 'davidjane' } ] var c = []; b.forEach(function(user) { var exists = false; for (let i=0; i<a.length && !exists; i++){ exists = a[i].username === user.username ; } c.push(Object.assign({},user,{exists})); }); console.log(c); 

Answer 2

First stringify a array. Loop through b and create a dynamic regex to test on a if the test matches do your stuff.

Hope this helps!

 var a = [{name:'john'},{name:'james'},{name:'jordan'},{name:'joe'}]; var b = [{name:'john'},{name:'joe'}, {name:'hello'}]; var strA = JSON.stringify(a) var result = b.map((el) => { var elStr = JSON.stringify(el) var regex = new RegExp(elStr, 'g') if(regex.test(strA)) return Object.assign({}, el, {exist: 1}) return Object.assign({}, el, {exist: 0}) }) console.log(result) 

Answer 3

You could use Array.every to check that every object in b is also in a , and in the callback you could use Array.some to check a for keys and values

 var a = [{name:'john'},{name:'james'},{name:'jordan'},{name:'joe'}]; var b = [{name:'john'},{name:'joe'}]; var exist = b.every( (o) => { let k = Object.keys(o)[0]; return a.some( p => k in p && p[k] === o[k]); }); console.log(exist) 

If you want to add properties, you can do that as well

 var a = [{name:'john'},{name:'james'},{name:'jordan'},{name:'joe'}]; var b = [{name:'john'},{name:'joe'}]; var c = b.map( (o) => { let k = Object.keys(o)[0]; return o.exist = a.some( p => k in p && p[k] === o[k]), o; }); console.log(c);