JS JavaScript: Var
Var is a keyword that is used to declare a variable.
But, you should NOT use var, use let when declaring a variable.
One of the most important things is that you should try to keep things simple!
JavaScript String Methods
JavaScript String Methods & Properties
JavaScript string (both primitive and String object) includes a bunch of default properties and methods that can be used for for different purposes.
The global object String is a constructor for strings or a sequence o characters.
String as an object
Everything in JavaScript is an object. For example when a string is created like this:
var myString = 'This is my string for testing';
the variable 'myString' becomes a string object instance. A string object instance has a vast number of properties and methods available to it.
String Methods
Here follows some useful methods that can be used.
| charAt() | Returns the character at the defined position. |
| charCodeAt() | Returns the Unicode of the character at the defined position. |
| concat() | Concatenate two or more strings, and returns a new concatenated string. |
| endsWith() | Checks if a string ends with the defined string or character. |
| fromCharCode() | Converts the Unicode values to characters. |
| includes() | Checks if a string contains the defined string/character. |
| indexOf() | Returns the first position where the defined value in a string is found. |
| lastIndexOf() | Returns the last position where the defined value in a string is found. |
| localeCompare() | Compares two strings. |
| match() | Search a string with a regular expression, and returns the matches |
| repeat() | Returns a defined number of copies of an existing string. |
| replace() | Search a string for a defined value, or a regular expression. If the value is found return a new string where the specified values is replaced. |
| search() | Search a string for a defined value, or a regular expression. If it's found the position of the match is returned. |
| slice() | Extracts a part of a string and return it as a new string. |
| split() | Split up a string into an array of substrings. |
| startsWith() | Checks if a string starts with the defined character/s |
| substr() | Return the characters from a string, beginning from a defined start position and from that position return the defined number of character. |
| substring() | Return the characters from a string, between two defined posistion. |
| toLocaleLowerCase() | Converts a string to the host's locale lowercase letters. |
| toLocaleUpperCase() | Converts a string to the host's locale uppercase letters. |
| toLowerCase() | Converts a string to lowercase letters. |
| toString() | Returns the value of a String object. |
| toUpperCase() | Converts a string to uppercase letters. |
| trim() | Trim both the start and the end of a string. |
| valueOf() | Returns the primitive value of a String object. |
String Properties
Here follows some useful properties that can be used.
| constructor | Returns the constructor function of a string. |
| length | Returns the length of a string |
| prototype | Use this to add properties and methods to an object |
Learn more about JavaScript Strings
Escape notations
When using special characters they can be encoded using escape notation:
\XXX |
octal Latin-1 character. |
\' |
single quote |
\" |
double quote |
\\ |
backslash |
\n |
new line |
\r |
carriage return |
\v |
vertical tab |
\t |
tab |
\b |
backspace |
\f |
form feed |
\uXXXX |
unicode codepoint |
\u{X} ... \u{XXXXXX} |
unicode codepoint |
\xXX |
Latin-1 character |
JavaScript is not like all other languages and makes no distinction between single-quoted strings and double-quoted strings. As a consquence of that strings created with either single or double quotes will behave the same.
HTML Wrapper Methods
To have the string wrapped inside a appropriate HTML tag the HTML wrapper methods can be used.
| anchor() | Is wrapping the string in a <a> tag. |
| big() | Is wrapping the string in a <big> tag. |
| blink() | Is wrapping the string in a <blink> tag. |
| bold() | Is wrapping the string in a <b> tag to make it bold in HTML. |
| fixed() | Is wrapping the string in a <tt> tag. |
| fontcolor() | Is wrapping the string in a <font color="color"> tag. |
| fontsize() | Is wrapping the string in a <font size="size"> tag. |
| italics() | Is wrapping the string in a <i> tag. |
| link() | Is wrapping the string in a <a>tag where href attribute value is set to specified string. |
| small() | Is wrapping the string in a <small>tag. |
| strike() | Is wrapping the string in a <strike> tag. |
| sub() | Is wrapping the string in a <sub>tag |
| sup() | Is wrapping the string in a <sup>tag |
Have in mind that these may not work as expected in all browsers since they are not standard methods.
Learn more about JavaScript Scope
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JS JavaScript: Scope
Scope determines if variables are accessible (visible).
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It is possible to comment code as a single-line comment or as a multi-line comment.
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JavaScript is one of the 3 core language technologies of the World Wide Web that all web developers must learn:
1. HTML to define the content of web pages.
2. CSS to specify the layout of web pages.
3. JavaScript to program the behavior of web pages.
JavaScript is a scripting or programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at, displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. − you can bet that JavaScript is probably involved. The benefits of using JavaScript are: 1. You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server. 2. Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something. 3. Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard. 4. Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.
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Developer Week
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