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# JavaScript Cheat Sheet — Operators and Dates

JavaScript is one of the most popular programming languages for web programming.

In this article, we’ll look at the basic syntax of modern JavaScript.

### Operators

We can do arithmetic with JavaScript.

We add with `+` and subtract with `-` :

``````let a = b + c - d;
``````

We multiply with `*` and divide with `/` :

``````let a = b * (c / d);
``````

And we get the remainder of one number divided by another with `/` :

``````let x = 100 % 48;
``````

We increment with `++` :

``````a++;
``````

And we decrement with `--` :

``````b--;
``````

### Typeof

We can get type of primitive values and objects with `typeof` :

``````typeof a
``````

It’s mostly useful for primitive values since it returns `'object'` for all objects.

### Assignment

We assign one value to a variable with `=` :

``````let x = 10
``````

The right expression is assigned to the variable on the left.

`a +=b` is short for `a = a + b` . We can also replace `+` with `-` , `*` and `/` .

### Comparison

We compare equality with `===` :

``````a === b
``````

We check for inequality with `!==` :

``````a !== b
``````

We check if `a` is greater than `b` with:

``````a > b
``````

And we check if `a` is less than `b` with:

``````a < b
``````

We can check for less than or equal with:

``````a <= b
``````

And we check for greater than or equal with:

``````a >= b
``````

Logical AND is `&&` :

``````a && b
``````

And logical OR is `||` :

``````a || b
``````

### Dates

We can create date objects with the `Date` constructor:

``````let d = new Date("2017-06-23");
``````

If we omit the month and day, then it’s set to January 1:

``````let d = new Date("2017");
``````

We can add the hour, minutes, and seconds with:

``````let d = new Date("2017-06-23T12:00:00-09:45");
``````

``````let d1 = new Date("June 23 2017");
let d2 = new Date("Jun 23 2017 07:45:00 GMT+0100 (Tokyo Time)");
``````

A date object comes with methods to let us get various values from it.

We call them by writing:

``````let d = new Date();
let a = d.getDay();
``````

`getDay()` gets the day of the week

`getDate()` gets the day of the month as a number.

`getFullYear()` gets the 4 digit year.

`getHours()` gets the hours.

`getMilliseconds()` gets the milliseconds.

`getMinutes()` gets the minutes.

`getMonth()` gets the month.

`getSeconds()` gets the seconds.

`getTime()` gets the milliseconds since 1970, January 1.

We can also set values with some setter methods.

To call them, we write:

``````let d = new Date();
d.setDate(d.getDate() + 7);
``````

`setDay()` sets the day of the week

`setDate()` sets the day of the month as a number.

`setFullYear()` sets the 4 digit year.

`setHours()` sets the hours.

`setMilliseconds()` sets the milliseconds.

`setMinutes()` sets the minutes.

`setMonth()` sets the month.

`setSeconds()` sets the seconds.

`setTime()` sets the timestamp.

### Conclusion

JavaScript comes with various operators and the `Date` constructor to let us create, get, and set dates. ## By John Au-Yeung

Web developer specializing in React, Vue, and front end development.