JavaScript Program
A computer program is a list of instructions executed by the computer. In programming languages these instructions are called statements. A JavaScript program is a list of statements
Basic Commands in JavaScript
JavaScript statements include
- Values
- Operators
- Expressions
- Keywords
- Comment
Semicolons (semicolon) in JavaScript
The statements in JavaScript are separated by semicolons.
Semicolon hides the end of statements in JavaScript
For example
1 2 3 4 5 | <span class="token keyword">let</span> x <span class="token punctuation">,</span> y <span class="token punctuation">,</span> z <span class="token punctuation">;</span> x <span class="token operator">=</span> <span class="token number">2</span> <span class="token punctuation">;</span> y <span class="token operator">=</span> <span class="token number">4</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> x <span class="token punctuation">,</span> y <span class="token punctuation">,</span> z <span class="token punctuation">)</span> <span class="token punctuation">;</span> |
We can write multiple statements on the same line if they are separated by semicolons.
Whitespace in Javascript
JavaScript does not care about the spaces in the code, so we can add spaces to make the code more readable.
For example
1 2 3 | <span class="token keyword">let</span> personName <span class="token operator">=</span> <span class="token string">"Nguyen CHi Hao"</span> <span class="token punctuation">;</span> <span class="token keyword">let</span> age <span class="token operator">=</span> <span class="token number">22</span> <span class="token punctuation">;</span> |
Command Blocks in JavaScript
JavaScript statements can be grouped together into code blocks inside {}.
The purpose of these blocks of code is to define statements to be executed together.
We can easily see blocks of code everywhere in the JavaScript code.
For example
1 2 3 4 5 6 | <span class="token keyword">function</span> <span class="token function">printPersonInfo</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> <span class="token string">"Tên:"</span> <span class="token punctuation">,</span> <span class="token string">"Nguyen Chi Hao"</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> <span class="token string">"Tuoi:"</span> <span class="token punctuation">,</span> <span class="token number">22</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> |
JavaScript Keywords
JavaScript statements are usually started with keywords. Here are some frequently used keywords in JavaScript code:
- var: declares a variable.
- let: declares a block scoped variable.
- const: declares a variable as a constant.
- if: Marks a block of statements to be executed when a condition is met.
- switch: Marks a block of commands to be executed when a condition is satisfied.
- for: Marks a block of statements to be executed in one round.
- function: Declare a function.
Conclude
Through the above article, we have known some frequently used statements in JavaScript code. In the next sections, I will go into detail about each concept in JavaScript. Thank you for reading, see you in the next part.