ConsolePrint to console | console.log(...)
|
CommentsOne line | // single line comment
| Multi lines | /*
A multi line comment
*/
|
Data Typesnumber
| 3, 3.1, -3.1, 3e5, 3e-5 | string
| "abc", 'abc', "", '' | boolean
| true, false | undefined
| No value | null
| Value of nothing | NaN
| Not a number |
Numbersvar x = 3.1415;
| Declare a number | x.toFixed(2)
| To string, fixed decimals | parseInt("2")
| Convert a string to int | parseFloat("1.23")
| Convert a string to float |
Stringsvar s = "Hello"
| Declare and assign a string | s.length
| Length of string | s.charAt(0)
| Access a character at index | s.indexOf("el")
| Index of a substring | s.slice(2, 4)
| Part of string (start, end) |
Arithmetic Operators+, -, *, /
| Add, subtract, multiply, divide | %
| Modulus (reminder) | =
| Assignment | ++, --
| Increment, decrement | +=, -=, *=, /=, %=
| Operation and assignment | ?
| a = (x > y)? b: c;
|
Comparisons==, !=
| Equal to, not equal | ===, !==
| with type | >, <, >=, <=
| Greater/Less or equal | &&, ||, !
| And, Or, Not |
FunctionsDeclare a function | function myFunc(p1, p2) {
statements;
return p1 + p2;
}
| Use a function | x = myFunc(1, 5);
| Function variable | var f = function(p1, p2) {
statements;
return p1 + p2;
};
| Use function varialbe | x = f(1, 5);
|
| | Conditionalsif | if (x > y) {
statements;
}
| if..else | if (x > y) {
statements;
} else {
statements;
}
| if..else if | if (x > y) {
statements;
} else if (x > z) {
statements;
} else {
statements;
}
| switch..case | switch(x) {
case 1:
statements;
break;
case 2:
statements;
break;
default:
statements;
}
|
Loopswhile
| var x = 0;
while (x < y) {
statements;
++x;
}
| for
| for (var x = 0; x < y; ++x) {
statements;
}
| continue
| Stop current iteration, continue with next one | break
| Stop loop immediately | for/in
| var x = [ "abc", "efg", "hij" ];
for (i in x) {
statements; // i = 0,1,2...
}
| for/of
| var x = [ "abc", "efg", "hij" ];
for (i of x) {
statements; // i = "abc","efg",..
}
|
Arraysvar a = [8, "hi", 6]
| Declare and assign | var a = []
| Declare empty array | a[0]
| Extract the first element | a[0] = "xx"
| Set the first element | a.length
| Length of array | a.push(17)
| Add element to array | a.pop()
| Remove the last element | a.splice(
s, r,
e1, e2..)
| From index s, remove r elements, then add e1, e2... | a.forEach(f)
| Run function f(e) for each element in array |
ObjectsLiteral object | var x = {
name: "cool",
size: 10,
sayHi = function() {
console.log(this.name);
}
}
| Constructor | function MyObj(nm) {
this.name = nm;
this.size = 10;
this.sayHi = function() {
console.log(this.name);
}
}
| Create new object | var x = new MyObj("cool");
| Use object | console.log(x.size);
x.sayHi();
|
|
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