Javascript Arrays

Array Length

Length Property and Not a Method

• Array length is a property array.length
• Array length is not a method array.length()
• Data Type: It is an unsigned, 32-bit integer with a maximum value of 2³² - 1 (Max: 4,294,967,295)
• Non-Numeric Indices: Adding properties to an array using strings
  • e.g.: arr["sample"] = "NewValue"
  • treated as object properties
  • does not affect the length property

Array resize using array.length

• Array can be resized by assigning value to the length property array.length = array.length + 3
• Assigning lesser value than the actual length will make the array shorter array.length = array.length - 3
• Setting array.length = 0 will clear the array and make it zero length, empty array.
• Negative value or a non-integer to length array.length = -3 will throw "RangeError"

Array Length

const data = ['first', 'second', 'third'];
console.log(data.length); // Output: 3

Array shorten

const data = ['first', 'second', 'third'];
data.length = 2;
console.log(data); // Output: ['first', 'second'];

Last Element

const data = ['first', 'second', 'third'];
console.log(data[length-1]); // Output: third

Remove empty string or falsey from an Array

To remove empty string or falsey values from an array, filter option could be used.

Filter Array with empty string ""

• If only empty string literals ("") are to be removed
• This will keep other values like 0 or null

Sample Code

let data = ["first", "", "third", "", "fifth"];

const newData = data.filter(item => item !== "");
//const newData = data.filter((item) => { return item !== ""});

console.log(newData) // Output: ["first", "third", "fifth"]

Filter Array all Falsey values

• It removes "" , null , undefined , 0 , false and NaN

Sample Code

let data = ["first", "", "third", "", "fifth"];

const newData = data.filter(Boolean);

console.log(newData) // Output: ["first", "third", "fifth"]

Array - check elements

Check "Every" array elements

Check each array element follows certain logic.

Sample Code

const data = [1, 2, 3, 4];

// Check if all numbers are greater than 0
// const output = data.every(element => element > 5);
const output = data.every((element,index,array) => {
    return  element > 0
});

console.log(output); // true

Check if "Some" array elements follow the rule

Check if at least one array element follows the rule.

Sample Code

const data = [-1, -2, 1, 2, 3, 4];

// Check if all numbers are greater than 0
// const output = data.some(element => element > 5);
const output = data.some((element,index,array) => {
    return  element > 0
});

console.log(output); // true