Iterables are iterable objects (like Arrays).
Iterables can be accessed with simple and efficient code.
Iterables can be iterated over with for..of loops
The JavaScript for..of statement loops through the elements of an iterable object. Continue reading JavaScript Iterables
The break statement “jumps out” of a loop.
The continue statement “jumps over” one iteration in the loop.
You have already seen the break statement used in an earlier chapter of this tutorial. It was used to “jump out” of a switch() statement.
The break statement can also be used to jump out of a loop:
for (let i = 0; i < 10; i++) {
if (i === 3) { break; }
text += "The number is " + i + "<br>";
}
In the example above, the break statement ends the loop (“breaks” the loop) when the loop counter (i) is 3. Continue reading JavaScript Break and Continue
Loops can execute a block of code as long as a specified condition is true.
The while loop loops through a block of code as long as a specified condition is true.
while (condition) {
// code block to be executed
}
In the following example, the code in the loop will run, over and over again, as long as a variable (i) is less than 10 :
while (i < 10) {
text += "The number is " + i;
i++;
}
If you forget to increase the variable used in the condition, the loop will never end. This will crash your browser.
The JavaScript for of statement loops through the values of an iterable object.
It lets you loop over iterable data structures such as Arrays, Strings, Maps, NodeLists, and more:
for (variable of iterable) {
// code block to be executed
}
variable – For every iteration the value of the next property is assigned to the variable. Variable can be declared with const, let, or var.
iterable – An object that has iterable properties. Continue reading JavaScript For Of
The JavaScript for in statement loops through the properties of an Object:
for (key in object) {
// code block to be executed
}
const person = {fname:"John", lname:"Doe", age:25};
let text = "";
for (let x in person) {
text += person[x];
}
Loops can execute a block of code a number of times.
Loops are handy, if you want to run the same code over and over again, each time with a different value. Continue reading JavaScript For Loop
The switch statement is used to perform different actions based on different conditions.
Use the switch statement to select one of many code blocks to be executed.
switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}
This is how it works:
Conditional statements are used to perform different actions based on different conditions.
Very often when you write code, you want to perform different actions for different decisions.
You can use conditional statements in your code to do this.
In JavaScript we have the following conditional statements :
if to specify a block of code to be executed, if a specified condition is trueelse to specify a block of code to be executed, if the same condition is falseelse if to specify a new condition to test, if the first condition is falseswitch to specify many alternative blocks of code to be executedThe switch statement is described in the next chapter.
A JavaScript Boolean represents one of two values: true or false.
Very often, in programming, you will need a data type that can only have one of two values, like
For this, JavaScript has a Boolean data type. It can only take the values true or false. Continue reading JavaScript Booleans
Math.random() returns a random number between 0 (inclusive), and 1 (exclusive):
// Returns a random number:
Math.random();
Math.random() always returns a number lower than 1.
Math.random() used with Math.floor() can be used to return random integers.
There is no such thing as JavaScript integers.
We are talking about numbers with no decimals here.