Użyj .Map do zliczania długości każdego elementu w tablicy
var lengths = chars.map(function(word){
return word.length
})
Wild Whale
var lengths = chars.map(function(word){
return word.length
}) var words = ['Hello', 'world'];
var lengths = words.map(function(word) {
return word + ' = ' + word.length;
});
console.log(lengths);let data = [ { "id": 1, "is_read": true, }, { "id": 2, "is_read": true, }, { "id": 3, "is_read": false, }, { "id": 4, "is_read": true, }, ],
length = data.filter(function(item){
return item.is_read;
}).length;
console.log(length)