JavaScript - Basics Concepts
{{lang-javascript}}let x = 10; |
block scope
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most used
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{{lang-javascript}}const MAX = 100; |
constant values
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{{lang-javascript}}var y = 10; |
global or function scope
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old usage
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{{lang-javascript}}let x = 10; |
assignment
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{{lang-javascript}}x == "Hello" |
comparison
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{{lang-javascript}}x === "Hello" |
strict comparison
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{{lang-javascript}}&& |
logical AND
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{{lang-javascript}}|| |
logical OR
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{{lang-javascript}}! |
logical negation
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{{lang-javascript}}let num = 10; |
Number
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{{lang-javascript}}let str = "Hello"; |
String
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{{lang-javascript}}let isTrue = true |
Boolean
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{{lang-javascript}}let arr = [1, 2, 3] |
Array
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{{lang-javascript}}let obj = { a:1, b:2, c:"three" } |
Object
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{{lang-javascript}}let array = ["a","b","c"] |
array definition
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{{lang-javascript}}array.length //3 |
number of elements in array
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{{lang-javascript}}array[0] // a |
access first element
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{{lang-javascript}}array[n] //0=<n<array.length |
access nth element
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{{lang-javascript}}array[4] // error |
4 grater then length of array
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{{lang-javascript}}array[array.length - 1] // c |
access last element
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{{lang-javascript}}// this is a one line comment |
{{lang-javascript}}/* this is a multiple |
{{lang-javascript}}let object = {
name: "Alice",
age: 30
}
{{lang-javascript}}object.name // Alice |
dot notation
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{{lang-javascript}}object["name"] // Alice |
property access notation
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{{lang-javascript}}object.age // 30 |
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{{lang-javascript}}object.gender // undefined |
non-existent property
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{{lang-javscript}}try{
//code might throw an error
} catch(err) {
console.error("Error occurred", err.message);
} finally {
console.log("Operation completed");
}{{lang-javascript}}function greet() {
console.log("Hello")
}{{lang-javascript}}function greet(name="Alice") {
console.log("Hello")
}No comments yet.
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