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最新评论
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hymzjsw:
python 变量命名规范 -
IWSo:
...
mysql #1170错误(42000) BLOB/TEXT Column Used in Key Specification Without a Key Le -
wl59138528:
由于Python臭名昭著的GIL问题,OpenERP 6.1以 ...
OpenERP 部署环境使用说明 -
greybeard:
xiaoyao3857 写道怎么看着一大堆,似乎中间有些东西重 ...
python 变量命名规范 -
xiaoyao3857:
怎么看着一大堆,似乎中间有些东西重复说了吧
python 变量命名规范
1. JS is a high-level, dynamic, untyped interpreted programming
language that is well-suited to object-oriented and functional
programming styles.
2.
3. Two other very important types that JavaScript programs can
manipulate are objects and arrays.
4.
5.
language that is well-suited to object-oriented and functional
programming styles.
2.
// variable is a symbolic name for a value. var x; // Declar a variable named x. x = 0; x x = 1; x = 0.01; x = "hello world"; x = 'JavaScript'; x = true; // Boolean values. x = false; x = null; // Null is a special value that means "no value". x = undefined; // Undefined is like null.
3. Two other very important types that JavaScript programs can
manipulate are objects and arrays.
// JavaScript's most important data type is the object. // An object is a collection of name/value pairs, or a string to // value map. var book = { // Objects are enclosed in curly braces. topic: "JavaScript", // The property "topic" has value "JavaScript". fat: true // The propery "fat" has value true. }; // Access the properties of an object with . or[]: book.topic // => "JavaScript" book["fat"] // => true: another way to access property values. book.author = "Flanagan"; // Create new properties by assignment. book.contents = {}; // {} is an empty object with no properties. // JavaScript also supports arrays (numerically indexed lists) of values: var primes = [2. 3, 5, 7]; // An array of 4 values, delimited with [ and ]. primes[0] // => 2: the first element (index 0) of the array. primes.length // => 4: how many elements in the array. primes[primes.lenght-1] // => 7: the lastelement of the array. primes[4] = 9; // Add a new element by assignment. primes[4] = 11; // Or alter an existing element by assignment. var empty = []; // [] is an empty array with no elements. empty.lenght // => 0 // Arrays and objects can hold other arrays and objects: var points = [ // An array with 2 elements. {x:0, y:0}, // Each element is an object {x:1, y:1} ]; var data = { // An object with 2 properties trial1: [[1,2], [3,4]], // The value of each property is an array. trial2: [[2,3], [4,5]] // The elements of the arrays are arrays. };
4.
// Operators act on values (the operands) to produce a new value. // Arithmetic operators are the most common: 3 + 2 // => 5: additon 3 - 2 3 * 2 3 / 2 points[1].x - points[0].x // => 1: more complicated operands work, too "3" + "2" // => "32": + adds numbers, concatenates strings // JavaScript defines some shorthand arithmetic operators var count = 0; // Define a variable count++; // Increment the variable count--; // Decrement the variable count += 2; // Add 2: same as count = count + 2; count *= 3; // Multiply by 3: same as count = count * 3; count // => 6: variable names are expressions. too // Equality and relational operators test whether two values are equal, // unequal, less than, greater than, and so on. They evaluate to true or false. var x = 2, y = 3; // These = signs are assignment, not equality tests x == y // => false: equality x != y // => true: inequality x < y // => true: less-than x <= y x > y "two" == "three" // => false: the two strings are different "two" > "three" // => true: "tw" is alphabetically greater than "th" false == (x > y) // => true: false is equal to false // Logical operators combine or invert boolean values (x == 2) && (y == 3) // => true: both comparisons are true. && is AND (x > 3) || (y < 3) // => false: neither comparison is true. || is or !(x == y) // => true: ! inverts a boolean value
5.
// Functions are parameterized blocks of JavaScript code that we can invoke. function plus1(x) { // Define a function named "plus1" with parameter "x" return x+1; // Return a value one larger than the value passed in } // Functions are enclosed in curly braces plus1(y) // => 4: y is 3, so this invocation returns 3+1 var square = function(x) { // Functions are values and can be assigned to vars return x*x; // Compute the function's value }; // Semicolon marks the end of the assignment. square(plus1(y)) // => 16: invoke two functions in one expression
发表评论
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JavaScript ---- 示例(十进制转换为二进制)
2012-01-17 23:15 3923<html> <head> ... -
JavaScript ---- Type Conversions
2012-01-16 23:27 1118JavaScript is very flexible abo ... -
JavaScript ---- Wrapper Objects
2012-01-14 23:41 1243We've also seen that strings ha ... -
JavaScript ---- The Global Object
2012-01-14 23:41 10461. The global object is a regul ... -
JavaScript ---- null VS undefined
2012-01-14 23:41 1038共同点: 1, null and undefined both ... -
JavaScript-----需要留心之处
2012-01-06 10:55 8161. === if (o !== null) ... -
JavaScript ---- Core constructor
2012-01-06 08:27 10731, Date var then = new Date( ... -
JavaScript----数字, 字符串, 布尔类型
2012-01-06 00:51 11301. 数字类型(numbers) 1.1 javascr ... -
JavaScript----变量
2012-01-06 00:21 7381. JavaScript变量是无类型的(untyped) ... -
JavaScript ---- Types
2012-01-05 16:14 8441. JavaScript types can be divi ... -
JavaScript ---- All Literals
2011-12-30 10:43 70412 // The ... -
JS类似命名空间制作
2011-11-30 10:26 1053// 创建一个默认的,全局的命名空间 var YAHOO ... -
JS继承
2011-11-30 09:44 11561. 原型式继承 // ... -
JS重要的地方
2011-11-30 09:14 899在JavaScript里,作用域是由函数划分的,而不是由块(b ... -
Preface
2011-11-24 09:48 973This book is divided into four ... -
JS 对象
2011-11-23 17:53 13181. JavaScript的简单类型包括数字,字符串,布尔值( ... -
JavaScript 基础语法
2011-11-19 11:25 10421. JavaScript 只有一个单一的数字类型。它在内部被 ...
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