Array Iteration

We can use a for loop to iterate through an array, but JavaScript arrays have built in methods we can also use…

let animals =  [
    { name : ‘Bongo’},
    { name : ‘George’}
];
animals.forEach(animal => console.log(animal)); 

This will iterate over each item in the array and output it to the console.

Remember that arrays are zero-based. There are times when we wish to access the index number of an array. forEach allows us to do just that…

animals.forEach((animal, index) => console.log(animal, index)); 

In this case, in addition to the animal names, we will get zero (0) and one (1) for each index of each item within the array.

Another method is “filter”…

let animals =  [
    { name : ‘Bongo’},
    { name : ‘George’}
];
let bongoGorilla = animals.filter(animal => animal.name === ‘Bongo’);
console.log(bongoGorilla); 

This will iterate over the array and return any item filtered out by the filter method. In this case, it return any animals with the name “Bongo”.

Another method is “every”…

let animals =  [
    { name : ‘Bongo’},
    { name : ‘George’}
];
let bongoGorilla = animals.every(animal => animal.name === ‘Bongo’);
console.log(bongoGorilla); 

This method returns a Boolean. It iterates over the array and performs the test on every item. In this case, we are testing if all animals are names “Bongo”. This will return false. It is a way to verify if an array contains the required data for your program.

Another method is “find”, which returns the first element found in an array using whatever criteria it is passed…

let animals =  [
    { name : ‘Bongo’},
    { name : ‘George’}
];
let georgeGorilla = animals.find(animal => animal.name === ‘George;);
console.log(georgeGorilla); 

In this case, we are looking for the first element in the array that has the name value of “George”. Find will iterate over the array until it finds the data and then will stop and return it. If it doesn’t find anything, it will return undefined.

Happy Coding!

Clay Hess