This is a recent study note for learning the basics of JavaScript
I am currently learning Web API. If I have time during the study, I will also post my own experience.
1. Introduction to Java Script
JS is divided into three parts:
while the basic syntax of javascript learned belongs to ECMAScript
2. Writing position
Same as CSS, there are three writing locations for JS: inline JS, embedded JS and external JS files
3. Input and output
In JS, the management of input and output is as follows:
only prompt() will pop up a window for the user to output, and both of them are output.
What we need to pay attention to is that the type of prompt input will be converted into a string. If we need other data types, we need to perform data type conversion, which will be discussed below.
Four. Variables
What are variables? Variables are actually equivalent to a container for storing data. We obtain and modify data through variable names.
It is a space that the program applies for in memory to store data, similar to a hotel or a room.
4.1 Use of variables
The first step is to declare the variable. Variables in JS need to be declared.
The second part is to assign values to variables:
Of course, we can also assign values when declaring variables, which we call variable initialization
4.2 Syntax extensions for variables
1. We can declare multiple variables at the same time. For example:
var age = 18,
name = '鸣人',
address = '火影村';
Like this, remove the last declared variable, separate each variable with a comma and break on a new line.
2. We usually declare and assign values to variables before outputting. However, consider the following three situations:
a. We only declare and do not assign values?
b. We do not declare, do not assign a value, and use it directly?
c. No declaration, only assignment?
What will be the result of the above three situations?
In the third case, we did not declare direct assignment, which is allowed, but we do not advocate such use, which will make the variable a global variable
4.3 Variable naming convention
