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While loop executes a set of statements as long as a condition is true. It requires relevant variables to be ready such as an indexing variable to iterate through a loop.

While Loop

Sample Codelet counter = 0;
while (counter < 10) {
	console.log(counter);
	counter++;
}

The for loop is C-style in that it requires three parts, the initialization or loop variant, the condition and advancement to next iteration. It is used to iterate over data when referring to a changing index.

For Loop

Sample Codelet even_numbers = [2,4,6,8,10];
for (let i = 0; i < even_numbers.length; i++) {
    let even_number = even_numbers[i];
    console.log(even_number + “\n”);
}
let names = [“Jake”, “John”, “James”];
for (let n = 0; n < names.length; n++) {
    let name = names[n];
    console.log(name + “\n”);
}

Loops execute one or more statements up to a specific number of times. Loops allow repetitive tasks to be executed using minimal code. Loops allow complex tasks to be simplified by automating similar operations.

Table : Loops

Table : Common Functions Used With Loops

Without Loops

Sample Codelet even_numbers = [2,4,6,8,10];
console.log(even_numbers[0]);
console.log(even_numbers[1]);
console.log(even_numbers[2]);
console.log(even_numbers[3]);
console.log(even_numbers[4]);
let names = [“Jake”, “John”, “James”];
console.log(names[0]);
console.log(names[1]);
console.log(names[2]);

JavaScript supports logical conditionals for mathematics in the form of comparison operators. Logical conditions are used to perform different actions based on different decisions.

JavaScript has the following conditional statements, if, else if, else and switch.

Use if to specify a block of code to be executed, if a specified condition is true.

If

Sample Codelet num1 = 10;
let num2 = 5;
if (num1 > num2) {
	console.log(“num1 is greater than num2”);
}

Use else if to specify a new condition to test, if the first condition is false.

Else if

Sample Codelet num3 = 11;
let num4 = 11;
if (num3 > num4) {
	console.log(“num3 is greater than num4”);
}
else if (num3 == num4) {
	console.log(“num3 and num4 are equal”);
}

Use else to specify a block of code to be executed, if the same condition is false.

Else

Sample Codelet num5 = 22;
let num6 = 33;
if (num5 > num6) {
	console.log(“num5 is greater than num6”);
} else if (num5 == num6) {
	console.log(“num5 and num6 are equal”);
}
else {
	console.log(“num5 is not greater than num6”);
}

Use switch to specify many alternative blocks of code to be executed. JavaScript uses switch case pair common in other programming languages. The break keyword stops the execution inside the switch block.

Switch

Sample Codelet num7 = 41;
let num8 = 77;
switch (true) {
	case (num7 > num8):
		console.log(“num7 is greater than num8”);
		break;
	case (num7 == num8):
		console.log(“num7 and num8 are equal”);
		break;
	default:
		console.log(“num8 is not greater than num7”);
}

An array specifies a variable that can be indexed as a list in rows and columns. The first index is zero as is common in most programming languages.

Arrays

Sample Codelet even_numbers = [2,4,6,8,10];
console.log(even_numbers);
console.log(even_numbers.length); // Number Of Items In List
console.log(even_numbers[1]); // Access Array Item By Index Number
even_numbers.pop(); // Remove Last Item
console.log(even_numbers);
even_numbers.push(10); // Add New Item At The End
console.log(even_numbers);
even_numbers.shift();  // Remove First Item
console.log(even_numbers);
even_numbers.unshift(2);  // Add New Item At The Beginning
console.log(even_numbers);
let even_numbers2 = [12, 14, 16];
let combined = even_numbers.concat(even_numbers2); // Merge 2 Arrays
console.log(combined);

Associate array stores a collection of named key and value pairs.

Associative Arrays

Sample Codelet pickup_truck = {“brand”:”Ford”, “model”:”F-Series”, “year”:1984};
console.log(pickup_truck.model);

A two-dimensional array is an array of arrays requiring two indices to select an element.

Two-dimensional Arrays

Sample Codelet int_array = [ [11,22,33], [111,222,333]];
let array2D =  [[“Ford”,”F-Series”,1984],[“GMC”,”C-Series”,1986]];
console.log(int_array);
console.log(array2D);

Multidimensional arrays are two or more levels deep containing one or more arrays.

Multidimensional Arrays

Sample Codelet students = {
    “john_doe” : {
        “name” : “John”,
        “surname” : “Doe”,
        “age” : 25
    },
    “jane_doe” : {
        “name” : “Jane”,
        “surname” : “Doe”,
        “age” : 25
    }
};
console.log(students);
console.log(students.john_doe.surname);

Table : Common Functions For Manipulating Lists

JavaScript logical operators are used to combine conditional statements. Each operand is a condition that can be evaluated to a true or false value. The value of the conditions determines the overall value of the operator or grouping.

Logical operators are use to control flow of the application. They are normally found as part of a control statement such as if and while.

Table : Logical Operators

Logical Operators

Sample Codelet num1 = 5;
let num2 = 10;
if ( num1 > 0 && num2 > 0 ) {
	console.log(“Both AND conditions are true”);
} else {
	console.log(“This condition grouping is false”);
}
if ( num1 > 0 || num2 > 0 ) {
	console.log(“At least one OR condition is true”);
} else {
	console.log(“Both conditions are false”);
}

JavaScript increment operators are used to increment a variable’s value and decrement operators are used to decrement a variable’s value. JavaScript supports pre- and post-increment and decrement operators allowing for the increment or decrement of the value by one.

Table : Increment And Decrement Operators

Increment And Decrement Operators

Sample Codelet num = 1;
num += 1; // Increment By One
console.log(num1); // Console Displays 2
num -= 1; // Decrement By One
console.log(num1); // Console Displays 1
num++; // Post-increment
console.log(num1); // Console Displays 2
num–; // Post-decrement
console.log(num1); // Console Displays 1

Comparison operators compare two values which can be numbers or strings.

Table : Comparison Operators

Comparison Operators

Sample Codelet name1 = “John”;
let name2 = “James”;
console.log(name1 == name2); // Console Displays False
console.log(name1 == 10); // Console Displays False
let num1 = 12;
let num2 = 22;
console.log(num1 > num2); // Console Displays False
console.log(num1 == 10); // Console Displays False

Assignment operators are used to assign a value to a variable or an expression. The assignment types can be arithmetic, logical, bitwise, shift, and compound operators.

Table : Assignment Operators

Assignment Operators

Sample Codelet num1 = 5;
let num2 = 3;
let num_add = num1;
num_add += num2;
let num_sub = num1;
num_sub -= num2;
let num_mul = num1;
num_mul *= num2;
let num_div = num1;
num_div /= num2;
let num_mod = num1;
num_mod %= num2;
let num_exp = num1;
num_exp **= num2;
console.log(num_add); // Console Displays 8
console.log(num_sub); // Console Displays 2
console.log(num_mul); // Console Displays 15
console.log(num_div); // Console Displays 1.66
console.log(num_mod); // Console Displays 2
console.log(num_exp); // Console Displays 125

The arithmetic operators perform addition, subtraction, multiplication, division, exponentiation, floor division and modulus operations.

Table : Arithmetic Operators

Arithmetic Operators

Sample Codelet num1 = 5;
let num2 = 3;
let num_add = num1 + num2;
let num_sub = num1 – num2;
let num_mul = num1 * num2;
let num_div = num1 / num2;
let num_mod = num1 % num2;
let num_exp = num1 ** num2;
let num_flo = Math.floor(num1 / num);
console.log(num_add); // Console Displays 8
console.log(num_sub); // Console Displays 2
console.log(num_mul); // Console Displays 15
console.log(num_div); // Console Displays 1.66
console.log(num_mod); // Console Displays 2
console.log(num_exp); // Console Displays 125
console.log(num_flo); // Console Displays 1