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5.3 JS Random

Math.random() returns a random number between 0 (inclusive), and 1 (exclusive):

Example 1: JS Math.random()

Math.random();              // returns a random number

Math.random() always returns a number lower than 1.

JavaScript Random Integers

Math.random() used with Math.floor() can be used to return random integers.

Example 2: JS Math.floor(Math.random() * 10)

Math.floor(Math.random() * 10);     // returns a random integer from 0 to 9

Example 3: JS Math.floor(Math.random() * 11)

Math.floor(Math.random() * 11);      // returns a random integer from 0 to 10

Example 4: JS Math.floor(Math.random() * 100)

Math.floor(Math.random() * 100);     // returns a random integer from 0 to 99

Example 5: JS Math.floor(Math.random() * 101)

Math.floor(Math.random() * 101);     // returns a random integer from 0 to 100

Example 6: JS Math.floor(Math.random() * 10) + 1

Math.floor(Math.random() * 10) + 1;  // returns a random integer from 1 to 10

Example 7: JS Math.floor(Math.random() * 100) + 1

Math.floor(Math.random() * 100) + 1; // returns a random integer from 1 to 100

A Proper Random Function

As you can see from the examples above, it might be a good idea to create a proper random function to use for all random integer purposes.
This JavaScript function always returns a random number between min (included) and max (excluded):

Example 8: JS Math.random() getRndInteger part 1

function getRndInteger(min, max) {
  return Math.floor(Math.random() * (max - min) ) + min;
}

This JavaScript function always returns a random number between min and max (both included):

Example 9: JS Math.random() getRndInteger part 2

function getRndInteger(min, max) {
  return Math.floor(Math.random() * (max - min + 1) ) + min;
}

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Module 5. Dates, Math and Random

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JS Dates Using new Date() part 1 JS Dates new Date() part 1 JS Dates new Date() part 2 JS Dates new Date() part 3 JS Dates new Date() part 4 JS Dates new Date() part 5 JS Dates new Date() part 6 JS Dates new Date() part 7 JS Dates new Date() part 8 JS Dates new Date() part 9 JS Dates Using new Date() string JS Dates Using new Date() part 2 JS Dates Using new Date() part 3 JS Dates Using new Date() part 4 JS Dates Using new Date() part 5 JS Dates The toString() Method JS Dates The toUTCString() Method JS Dates The toDateString() Method JS Dates The toISOString() Method JS Dates ISO Dates part 1 JS Dates ISO Dates part 2 JS Dates ISO Dates part 3 JS Dates ISO Dates part 4 JS Dates ISO Dates part 5 JS new Date() part 1 JS new Date() part 2 JS new Date() part 3 JS new Date() part 4 JS new Date() part 5 JS new Date() part 6 JS Date.parse() part 1 JS Date.parse() part 2 JS Dates The getTime() Method JS The getFullYear() Method JS The getMonth() Method part 1 JS The getMonth() Method part 2 JS The getDate() Method JS The getHours() Method JS The getMinutes() Method JS The getSeconds() Method JS The getMilliseconds() Method JS The getDay() Method part 1 JS The getDay() Method part 2 JS setFullYear() part 1 JS setFullYear() part 2 JS setMonth() JS setDate() part 1 JS setDate() part 2 JS setHours() JS setMinutes() JS setSeconds() JS Compare Dates JS Math.PI JS Math.round() JS Math.pow() JS Math.sqrt() JS Math.abs() JS Math.ceil() JS Math.floor() JS Math.sin() JS Math.cos() JS Math.min() JS Math.max() JS Math.random() JS Math Constants JS Math.floor(Math.random() * 10) JS Math.floor(Math.random() * 11) JS Math.floor(Math.random() * 100) JS Math.floor(Math.random() * 101) JS Math.floor(Math.random() * 10) + 1 JS Math.floor(Math.random() * 100) + 1 JS Math.random() getRndInteger part 1 JS Math.random() getRndInteger part 2