What is the syntax in this filter method?

What is the syntax in this filter method?
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Could anybody help me explain the syntax of {name} in the following example?

When I use filter method, I always set the callback function as function(item){...} or item => {...}. But in the example, the author set the parameter of callback function as ({name}). What is the syntax rule?

function countBy(items, groupName) {

    let counts = [];
    for (let item of items) {
        let name = groupName(item);
        let known = counts.findIndex(c => c.name == name);
        if (known == -1) {
                count: 1
        } else {

    return counts;


let myArray = [1, 2, 3, 4, 5]; 

function moreThanTwo(n) {
    return n > 2;

console.log(countBy(myArray, moreThanTwo).filter(({name}) => name != false));
console.log(countBy(myArray, moreThanTwo).filter((item) => item.name != false)); // I would set the parameter in this way.

I come across this example in book Eloquent JavaScript (page 94) and make some alteration for clarification. The countBy function expects a collection (anything that we can loop over with for/of) and a grouping function. It returns an array of objects, each of which names a group and tells you the amount of elements that were found in that group.


He is doing object destructuring, an ES6 feature.

He is saying "the CB in filter is being send an object with a property name - please take out that property and assign it to a variable called name.

The same thing could have been accomplished with:

console.log(countBy(myArray, moreThanTwo).filter((obj) => obj.name != false));


Many thanks!:grinning:


That’s why we’re here. :wink: