##String
” and ‘
var name = 'tangkikodo';
var statment = "this is kikodo's string";
var statment2 = 'He is a "freak"';
var statment3 = "escape here: \"this is kikodo\' string\""
###escape
var path = "C:\\folder\\myfile.c";
var multiline = "this is a long\
string";
var multiline2 = "this is line1\nthis is line2\n";
###join
var part1 = "hello ";
var part2 = "world";
var all = part1 + part2;
###string method
var length = "hello world".length;
var index = "hello world".indexOf("world"); //World-> -1
console.log("hello".charAt(2));
console.log("hello".substr(1, 2)); //start, length
console.log("HELLO".toLowerCase()); //origin str do not change
console.log("HELLO".toUpperCase()); //origin str do not change
###string compares
var first = "hello";
var second = "Hello";
// == will change type
if (first.toLowerCase() === second.toLowerCase()) {
console.log("the strings are equal");
} else {
console.log("the strings are different");
}
function compare(a, b) {
console.log(a + '<' + b , a < b);
}
compare('a', 'b'); // true
compare('a', 'A'); // false 0x41, 0x31
compare('apple', 'orange'); // compare one by one. and substr lose
compare('app', 'app') //false ,if <= will be equal
##Numbers
only one type of number
var a = 11,
b = -123;
var c = 1.5,
d = 123.4321;
var e = 0.1,
f = 0.2;
var result = e * f;
//0.0200000000000000004 , near but not..
###advance
var g = 10E6;
var h = 1.23E6;
var i = 012; // oct 12 -> 10
var ii = 019; // auto change to decimal..
var j = 0x11; //heximal
##convert between string and number ###convert to whole number
var j = parseInt("197");
var jj = parseInt("012");
var jjj = parseInt("019"); // -> 1
//recommand way
var k = parseInt("019", 10); // -> 19
var l = parseInt("0100110", 2);
var m = parseInt("0100110", 3);
var n = parseInt("23 people", 10); //as much as it could
var o = parseFloat("123.45");
###NaN
var l = NaN;//false
l == l; //false
l === l; //false
l === NaN; //false
//use is NaN()
console.log(isNaN(l));
##Operations ###operate
var o = 1 + 2;
var q = 3 * 4.2;
var r = 16 / 8;
var s = 16 / 7;
var t = 15 % 10;
var u = (1 + 2) * (3 + 4);
operator precedence ###comparsion
console.log( 1 < 2);
console.log( 1 === 1.00); //true
console.log( 1 == "1"); //true ,auto change
console.log( 1 === parseInt("1", 10)); //true
console.log( 1 != 3); //true
console.log( 1 !== 3); //true
###math
var u = Math.random();
var u = Math.round(Math.random() * 10);
var u = Math.round(2.7); //upper from 2.5.
var u = Math.floor(2.9); // 2
var u = Math.ceil(6.2); // 7
var u = Math.pow(2, 5);
var u = Math.sqrt(4);
var u = Math.min(2, 4);
// type Math in Chrome's console, you can view all methods
##Array ###define
var x = ['some', 'word', 'here'];
x.length;
var y = ['string', 3, true, function (a,b) {return a + b}];
var z = ['string', ['substr', 2]];
var z = [];
var a = new Array();
var a = new Array(50); //define
###slice and operate
var word = y[0];
var answer = y[1];
var foo = y[3];
foo(1,2);
var ud = y[100]; //undefined
y[4] = 144;
y[20] = 21; //interval value -> undefined
y[y.length] = "new element";
y[y.length] = "new element";
y[y.length] = "new element"; //auto add at end
###methods
/*push and pop*/
var my_array = [2, 3, 4];
//log, otherwise it will be the same
console.log(my_array.toString());
my_array.push(5); //return current length
console.log(my_array.toString()); //log
var lastone = my_array.pop();
var lastone2 = my_array.pop();
/* unshift and shift*/
var my_array = [2, 3, 4];
console.log(my_array.toString()); // 2,3,4
my_array.unshift(1);
console.log(my_array.toString()); // 1,2,3,4
var my_array = [2, 3, 4];
console.log(my_array.toString()); // 2,3,4
my_array.shift();
console.log(my_array.toString()); // 3,4
###methods - sort
var my_array = [10 ,42, 12, 3, 0, 4, 11];
console.log(my_array.toString());
my_array.sort(function (a, b) {
return a - b; //-n, 0 , n
});
console.log(my_array.toString()); // itself is sorted, but.. string
//trick, mess it
my_array.sort(function (a, b) {
return Math.random() - 0.5;
});
var my_array = [1,2,3,4,5];
my_array.reverse();
//sorted by length
my_array.sort(function (a, b){
return a.length- b.length;
})
###method - concat
var x = [1,2,3];
var y = [5,6,7];
var z1 = x.concat(y); //concat(l1,l2,l3);
var z2 = x.concat(5,6,7); //same result
var z3 = x.concat(5,[6,7]); //like append with extend
###method - slice
var my_array = [0,1,2,3,4,5,6,7];
var result = my_array.slice(1, 4); //start & end
###method - join
var my_array = ['this', 'is', 'a', 'line' , 1, 2];
var result = my_array.join(' ');
compare with python
my_array = [1,2,3,4,5];
result = ' '.join(my_array) #it will raise TypeError
result = ' '.join(map(str, my_array))
###method - splice
var my_array = [0, 1, 2, 3, 4, 5, 6];
delete my_array[2]; //set to undefined
//from 2, remove 1 element
my_array.splice(2, 1);
//from 2, remove 0 element, add 1 element
my_array.splice(2, 0, 'two');
//from 2, remove 1 element, add 1 element
my_array.splice(2, 1, 'two');
my_array[2] = 'two';
//from 2, remove 0, add array
my_array.splice(2, 1, 'two', 'three', 'sth else');
##Functions ###basic functions
function sayHello (name, greeting) {
console.log(greeting + "hello" + name);
}
function sayHello (name, greeting) {
if (typeof greeting === "undefined"){
greeting = "Hello";
} //没有默认值的写法吗？
console.log(greeting + "hello" + name);
}
sayHello();
###return value
function sayHello (name, greeting) {
if (typeof name === "undefined") {
return 0;
}
if (typeof greeting === "undefined") {
greeting = "Hello";
}
console.log(greeting + "hello" + name);
return "Done";
//return name.length;
console.log("end of log"); //will not execute
}
###scope
//shadowing variable
var color = "black";
function showColor () {
var color = 'green';
shape = "square";
console.log(color);
}
showColor();
console.log("global shape", shape);
//global can be define inside function..
###anonymous functions
function myFunction () {
return "fine";
}
myFunction();
var myFunction = function () {
return "anonymous";
}
myFunction();
var callTwice = function (targetFunction) {
targetFunction();
targetFunction();
}
callTwice(myFunction);
callTwice(function () {
console.log("hahaha");
})
//useful in debug
callTwice(function namedFunction () {
console.log("hahaha");
})
(//only way to create a scope
function () {
var a, b, c;
//...
console.log("from anon functions");
})(1, 'hello');
###examples DOM
button = document.getElementById('action');
input = document.getElementById('text_field');
//onclick is good, but not good enough
button.onclick = function () {
console.log('aaa');
}
button.onclick = function () {
console.log('bbb');
} //will override last one..
//addEventListener is better
button.addEventListener('click', function () {
console.log('action1');
});
button.addEventListener('click', function () {
console.log('action2');
input.setAttribute('value', 'Hello world');
});
##Object ###basic
var kikodo = {"name": "kikodo"};
kikodo.name;
//better
var kikodo = {
name: "kikodo",
skills: ["ruby", "js"],
"favorite color": "green"
};
kikodo["favorite color"]
###method
var kikodo = {
name: "kikodo",
greet: function () {
console.log("hello, I am "+ kikodo.name); //not good
}
};
kikodo.greet();
var kikodo = {
name: "kikodo",
greet: function (person) {
console.log("hello, I am "+ person.name); //isn't ideal
}
};
kikodo.greet(kikodo.name);
var kikodo = {
name: "kikodo",
greet: function () {
console.log("hello, I am "+ this.name); //that's it
}
};
kikodo.greet();
var greet = kikodo.greet;
greet() // hello, I am DOMWindow
function WhatIsThis () {
console.log(this); //-> DOMWindow
}
###apply
var greet = kikodo.greet;
greet.call(kikodo); //bund to kikodo...
greet.call({}); //I am undefined
greet.call({"name": "Amit"}); //I am undefined
kikodo.greet.call({"name": "Amit"}); //holly shit, cool
kikodo.greet.call({"name": "Amit"}, "Matt", "bad"); // rest strings
kikodo.greet.apply(nick);
var jim = {
name: "jim";
greet: function (name, mood) {
name = name || "you";
mood = mood || "good";
console.log("hello," + name + " I am "
+ this.name + " and I am in a " + mood + " mood!");
}
}
jim.greet.apply(nick, ["Matt", "bad"]); //array!
var args = ["Matt", "bad"];
jim.greet.apply(jim, args);
###prototype1
var personPrototype = {
name: "Anonymous";
greet: function (name, mood) {
name = name || "you";
mood = mood || "good";
console.log("hello," + name + " I am "
+ this.name + " and I am in a " + mood + " mood!");
},
species: "Homo Sapien"
}
function Person (name) {
//constructor, Capitalized as convention
this.name = name;
return this; //default return this if no return..
}
Person.prototype = personPrototype; //it knows where prototype is
kikodo = new Person("kikodo")
//new: this !-> windows, this ->Person
//new: __proto__ -> personPrototype
//new: [name, __prototype__]
kikodo.greet()
###prototype2
Person.prototype.species = "Human"; //change things..
Person.prototype.favoriteColor = "red";
//personPrototype.favoriteColor = "red"; //same?
/* what happen if i forgot to add new */
kikodo = Person("kikodo"); //-> windows.name == "kikodo"