This section can't come soon enough for me and I am here now! The syntax of JS is similar to other programming languages which I study in my university.
null - data type that has no value (value of nothing, totally empty), return null if you purporsely assign value to nothing
undefined - absence of value, undefined will be returned if you do not assign value to var
NaN returns if you write square root of negative number.
When do such type of convertion == or != JS first converts each value to the same type, better use strict equality ==== first compare without type conversion.
The value inside if statement is always converted to true or false.
**List of falsy values: **
- false
- null
- undefined
- 0
- empty string
- Nan
Other values are truthy.
Ternary operator is shortcut for if statement
conditional ? (if condition is true) : (if condition is false)
It simplifies the code, but to my mind it is harder to read and understand that code with ternary operator. Hoisting in JS hoists function and variable declarations to the top of scope.
When function is stored inside a variable it is called function expression. When function keyword has no name it is called anonymous.
A function that is passed into another function is called callback. The most common case to pass named function as paramater. Anonymous can be used in event handlers :)
push -> add elements to the end of array, returns the length of the array after an element has been added.
pop -> remove elements from the end, returns the element that has been removed
splice -> allow to add and remove from anywhere in array
forEach -> manipulate each element of the array
When I was doing exersises on Udacity concerned to array method I tried to use inline function expression with forEach method and that is a little bit tricky.
map -> map returns new array with new values function calculated
Object in JS is like another data type.
Naming conventions for objects. * Do not use numbers as the first charachters in property name, hyphens and spaces* instead use camelCase :)
What was new ? Spread syntax like 3 dots before array, it can be used instead of .apply
Math.max(..arr);
//instead of
Math.max.apply(null,arr);
object arguments stores information about parameters
for ...in iterates over enumarable properties of object
Ohh, that was not easy, I have been solving tasks for 4 days , but it is great evolution! I learnt a lot of new methods in JS which facilitate a lot.
