Here is a cheat sheet on the basics of the Javascript language. I will be including conventions E5 to E9 as long they cover the basic markers as indicated in my Cheat Sheet: Bone Collection article where I compare the languages I use.
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BOF and EOF
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<script> /* start and end the code with these tags... */ </script>
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Documentation
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/**
* Function Name
* A description of the what the function is doing
* @param nameOfParameter1 data type
* ...
* @return data type
*/
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Single line comments
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// or #
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Multi line comments
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/* ... */
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EOL delimiter
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// End of limiter not needed for modern versions of the language
;
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Basic Output
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// basic output with the terminal or browser console
console.log("BlinkWiki")
console.warn("BlinkWiki")
console.error("BlinkWiki")
// output with an alert box
alert("Hello BlinkWiki!");
// output with a confirm box
if (confirm("Are you forgetting something about this language?")) {
console.log("Here is a cheat sheet!")
}
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DATATYPES
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Integer
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// numerical value from -2billion to +2billion, with no decimals
let count;
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Float
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// numerical value with decimal places
let count = 20.51;
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String
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// Collection of characters enclosed in quotes
let message = "BlinkWiki";
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Boolean
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// logical variable that has TRUE or FALSE as value
var isReady = true;
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Array
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// collection of items that can be referenced by indices
var words = ["Hello", "BlinkWiki"];
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Object
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// variable in key-value notation or instance of class
let blinkWiki = {
name: "BlinkWiki",
url: "www.blinkwiki.com",
pages:36
}
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Undefined
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// undefined variables have not been initialised
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Null
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// null variables do not been any values
let nullVariable = null;
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INITIALIZATION
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Initialization keywords
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// newer versions / frameworks of the language require let
let, var
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Naming variables
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variableName
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Naming constants
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constantName
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Initializing a constant
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const PI = 3.14
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Initializing an integer
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let count = 36
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Initializing a string
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let message = "Hello BlinkWiki"
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OPERATORS
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Operators
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+ // Addition
- // Subtraction
* // Multiplication
/ // Division
% // Modulus division
** // Raised to power
= Equation
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Logical Operators
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|| // Logical OR
&& // Logical AND
== // Logical Equation
=== // Is identical
!= // Logical Inequality
<> // Logical Inequality
!=== // Is not identical
< // Less than
> // Greater than
<= // Less than or equal to
>= // Greater than or equal to
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Assignment Operators
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+= // Add and assign
-= // Subtract and assign
*= // Multiply and assign
/= // Divide and assign
%= // Complete Modulus division and assign
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Increments and Decrements
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++count // Increase count and then return it
--count // Decrease count and then return it
count++ // Return count and then increase it
count-- // Return count and then decrease it
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String Operators
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Concatenation
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message = "Blink" + "Wiki"; // returns `BlinkWiki`
message += " Cheat Sheets"; // returns 'BlinkWiki Code Sheets'
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CONDITIONALS
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If ... ElseIf ... Else
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if (condition1) {
// run this if condition1 was met
} else if (condition2) {
// run this if condition2 was met
} else {
// run this if neither condition1 nor consition2 were met
}
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Switch ... Case
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switch (variable) {
case "One":
// variable == "One"
break;
case "Two":
// variable == "Two"
break;
case "Three":
// variable == "Three"
break;
default:
// variable is not "One", "Two" or "Three"
}
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LOOP CONSTRUCTS
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While
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i = 0;
// while this condition is still being met
while (i < 3) {
// TODO: provide the logic
i++;
console.log(i);
}
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Do While
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i = 0;
// start the loop
do {
// TODO: provide the logic
i++;
console.log(i);
// stop the loop when the condition below has been met
} while (i < 3);
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Foreach
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// define a collection
collection = array(0,1,2,3);
// start a loop to go through every item in a collection
foreach (collection as number) {
console.log(number);
}
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For
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// start the loop from i = 0 and stop when i<3
for (i=0; i<3, i++) {
console.log(i);
}
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CONSTRUCTS
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Function
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function greet() {
// TODO function logic goes here ...
}
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Function returning a variable
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function greet(parameter) {
// TODO function logic goes here ...
return "Hello BlinkWiki";
}
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Function with Parameter
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function greet(parameter) {
// TODO function logic goes here ...
}
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Function with Parameter
and default value
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function greet(parameter) {
// ensure the default value of parameter
parameter = (parameter === undefined) ? "BlinkWiki" : parameter
return "Hello " + parameter;
}
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Function with unknown
number of parameters
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function greet(...parameters) {
// TODO return the second parameter provided ...
return parameter[2];
}
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HANDLING ERRORS
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Try ... Catch ... Finally
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try {
// TODO: code that throws an exception on condition
} catch (Exception e) {
// TODO: inform user of the exception
} finally {
// TODO: logic that will run after the exception has been handled
}
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