Lesson 5 Async JavaScript | Promise

Event Loop

Video: Event Loop in JavaScript

Promises

Article: Promises

Async JavaScript

Article for just look through: async javascript

JavaScript string methods

charAt(index) - Returns the character at the specified index.
- Example:
```
"hello".charAt(1); // "e"
```
concat(...strings) - Combines the original string with one or more strings and returns the result.
- Example:
```
"hello".concat(" ", "world"); // "hello world"
```
includes(substring, start) - Checks if a string contains a specified substring, starting at an optional position.
- Example:
```
"hello world".includes("world"); // true
```
indexOf(substring, start) - Returns the index of the first occurrence of a substring, or -1 if not found.
- Example:
```
"hello world".indexOf("o"); // 4
```
lastIndexOf(substring, start) - Returns the index of the last occurrence of a substring, or -1 if not found.
- Example:
```
"hello world".lastIndexOf("o"); // 7
```
slice(start, end) - Extracts a section of the string and returns it as a new string.
- Example:
```
"hello world".slice(0, 5); // "hello"
```
substring(start, end) - Returns the part of the string between the start and end indices.
- Example:
```
"hello world".substring(0, 5); // "hello"
```
toLowerCase() - Converts the string to lowercase.
- Example:
```
"Hello World".toLowerCase(); // "hello world"
```
toUpperCase() - Converts the string to uppercase.
- Example:
```
"Hello World".toUpperCase(); // "HELLO WORLD"
```
trim() - Removes whitespace from both ends of the string.
- Example:
```
"  hello world  ".trim(); // "hello world"
```
split(separator, limit) - Splits a string into an array of substrings based on a separator.
- Example:
```
"hello world".split(" "); // ["hello", "world"]
```
replace(searchValue, newValue) - Replaces occurrences of a substring with a new string.
- Example:
```
"hello world".replace("world", "everyone"); // "hello everyone"
```
replaceAll(searchValue, newValue) - Replaces all occurrences of a substring with a new string.
- Example:
```
"hello world world".replaceAll("world", "everyone"); // "hello everyone everyone"
```
startsWith(substring, start) - Checks if the string starts with the specified substring.
- Example:
```
"hello world".startsWith("hello"); // true
```
endsWith(substring, length) - Checks if the string ends with the specified substring.
- Example:
```
"hello world".endsWith("world"); // true
```
repeat(count) - Repeats the string the specified number of times.
- Example:
```
"hello".repeat(3); // "hellohellohello"
```
padStart(targetLength, padString) - Pads the string at the start with the specified string until it reaches the target length.
- Example:
```
"5".padStart(3, "0"); // "005"
```
padEnd(targetLength, padString) - Pads the string at the end with the specified string until it reaches the target length.
- Example:
```
"5".padEnd(3, "0"); // "500"
```

Lesson 5 Async JavaScript | Promise | String Methods

Event Loop

Promises

Async JavaScript

JavaScript string methods