JavaScript Arrays

An array stores many values in one variable, in order. Each item has an index that starts from 0.

const fruits = ["apple", "banana", "mango"];

console.log(fruits[0]);
console.log(fruits[2]);
console.log(fruits.length);
console.log(fruits.at(-1));

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Add and remove items

Method	What it does
push(x)	Adds at the end
pop()	Removes the last item
unshift(x)	Adds at the start
shift()	Removes the first item
splice(start, count, ...items)	Removes or inserts items at a position
slice(start, end)	Copies a part, does not change the original

const list = ["a", "b", "c"];

list.push("d");
console.log(list);
list.pop();
list.unshift("z");
console.log(list);
list.splice(1, 1);        // remove 1 item at index 1
console.log(list);
console.log(list.slice(0, 2));

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Search and join

const nums = [10, 20, 30];
console.log(nums.includes(20));
console.log(nums.indexOf(30));
console.log(nums.join(" - "));
console.log([1, 2].concat([3, 4]));
console.log([...nums, 40]);

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Loop over an array

const colors = ["red", "green", "blue"];

for (const color of colors) {
  console.log(color);
}

colors.forEach((color, index) => {
  console.log(index + ": " + color);
});

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Summary

• Arrays hold ordered values and start at index 0.
• push/pop work at the end, unshift/shift at the start, splice anywhere.
• Loop with for...of or forEach.
• Next: Array Methods.

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