Operators

Note the two different uses of the equals sign: A single equals sign (=) is used to assign a value to a variable. A triple equals sign (===) is used to compare two values (see Equality Operators).

Equality operators

• Equality ==
• Inequality !=
• Identity / strict equality === (preferred)
• Non-identity / strict inequality !== (preferred)

How does this work in practice?

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1 == 1; // -> true
7 == "7"; // -> true
1 != 2; // -> true
5 === 5; // -> true
9 === "9"; // -> false
3 !== 3; // -> false
3 !== "3"; // -> true

why does 7 == '7' returns true and 9 === '9' returns false?

We strongly recommend that you always use the strict form when comparing for equality (===) or inequality (!==). Use the non-strict forms only when there is a compelling reason to do so (you will be hard pressed to find such a reason).

Relational operators

• Greater than operator >
• Greater than or equal operator >=
• Less than operator <
• Less than or equal operator <=

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4 > 3; // -> true
3 >= 3; // -> true
13 < 12; // -> false
3 <= 4; // -> true

More about comparison operators

• Addition +
• Subtraction -
• Multiplication *
• Division /
• Remainder (sometimes called modulo) %
  Returns the remainder left over after you've shared the left number out into a number of integer portions equal to the right number.

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8 + 9; // -> 17, adds two numbers together.
20 - 12; // -> 8, subtracts the right number from the left.
3 * 4; // -> 12, multiplies two numbers together.
10 / 5; // -> 2, divides the left number by the right.
8 % 3; /// -> 2, as three goes into 8 twice, leaving 2 left over.

More about Arithmetic operators

• AND &&
• OR ||

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true && false; //-> false
false && true; //-> false
false || true; //-> true
true || false; //-> true

Given that x = 6 and y = 3

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x < 10 && y > 1; // -> true
x === 5 || y === 5; // -> false
x !== y; // -> true

Logical NOT

• NOT !

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true === !false;
false === !true;

More about logical operators

typeof operator

To get the type of a value assigned to a variable, use the following code:

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let bar = 42;
typeof bar; //-> 'number'
typeof typeof bar; //->  'string'

So the data type of what typeof returns is always a string, bar on the other hand is still a number.

In addition to the simple assignment operator = there are also compound assignment operators such as +=. The following two assignments are equivalent:

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x += 1;
x = x + 1;

Also check out special characters and their names