Variables #

Declare #

var declares a new variable. = is the assignment operator.

var someVar = 'something or other';
console.log(some_var);
// outputs 'something or other'

^ convention for variable naming is camel case.

Newer way of assigning a variable than var.

Advantage over var: variable can be re-assigned later on.

let favoriteFood = 'apple';
console.log(favoriteFood);
// outputs 'apple'
favoriteFood = 'banana';
console.log(favoriteFood);
// outputs 'banana'

Can also create a variable without assigning anything:

let favoriteFood; // that's it

another way to do it, const is short for “constant”.

Difference from let - const can’t be re-assigned later on AND must be assigned a value upon creation.

Mathemetical operators can be used with variable assignment.

let thing = 1;
thing = thing + 1;
console.log(thing); // outputs 2

Another way to increment is with +=:

let thing = 1;
thing += 1; // same as above

Other operators:

Use +.

let stringVar = 'Sup';
console.log('stringVar' + ' cat')

Use template literals to interpolate (insert) strings. Syntax: ${variable} in the middle of a string, all wrapped by back-ticks.

let animal = 'turtles';
console.log(`I like ${animal}.`); // note the back-ticks

Super readable.

Variables have types (numerical, string, bool, etc). typeof shows the variable type.

const something = 1;
console.log(typeof something);

Variables are: