Compare two arrays of objects and remove items in the second one that have the same property value

Question

All I need to do is compare two arrays of objects and remove items in the second one that have the same property value. For example:

var a = [{'name':'bob', 'age':22}, {'name':'alice', 'age':12}, {'name':'mike', 'age':13}];
var b = [{'name':'bob', 'age':62}, {'name':'kevin', 'age':32}, {'name':'alice', 'age':32}];

function remove_duplicates(a, b) {
    for (var i = 0, len = a.length; i < len; i++) {
        for (var j = 0, len = b.length; j < len; j++) {
            if (a[i].name == b[j].name) {
                b.splice(j, 1);
            }
        }
    }

    console.log(a);
    console.log(b);

}

console.log(a);
console.log(b);

remove_duplicates(a,b);

I cannot understand why this does not work and instead gives:

Uncaught TypeError: Cannot read property 'name' of undefined

What I expected was the following content in b:

[{'name':'kevin', 'age':32}];

Answer 1

FIDDLE

 for (var i = 0, len = a.length; i < len; i++) { 
        for (var j = 0, len2 = b.length; j < len2; j++) { 
            if (a[i].name === b[j].name) {
                b.splice(j, 1);
                len2=b.length;
            }
        }
    }

Answer 2

Instead of using two loops you might also use the findIndex function:

for (var i = 0, len = a.length; i < len; i++) {
    var ItemIndex = b.findIndex(b => b.name === a[i].name);

    a.splice(ItemIndex, 1)
}

Or if you want to go completely without using a loop you might use the forEach function

a.forEach(function(item, index, array) {
    var ItemIndex = b.findIndex(b => b.name === item.name);

    a.splice(ItemIndex, 1)
}