下面的这个例子可能大家一看就知道答案了,因为闭包函数increment、decrement、value可以访问privateCounter,所以答案不言而喻了。 var counter = (function() { var privateCounter = 0; function changeBy(val) { privateCounter += val; } return { incr
increment()、decrement()、value()这三个公共函数是共享同一个作用域执行上下文环境的变量对象, 也就是闭包也多亏js的作用域,它们都可以访问privateCounter变量和changeBy函数 应用场景2 在内存中保持变量数据一直不丢失! 还是以最开始的例子, 由于闭包的影响,函数outerTest中num变量会一直存在于内存中,因此每次执行外...
var Counter = (function() { var privateCounter = 0; function changeBy(val) { privateCounter += val; } return { increment: function() { changeBy(1); }, decrement: function() { changeBy(-1); }, value: function() { return privateCounter; } } })(); console.log(Counter.value())...
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, // ...
示例9-1 演示了定义 JavaScript 类的一种简单方法。然而,这并不是惯用的做法,因为它没有定义构造函数。构造函数是为新创建的对象初始化而设计的函数。构造函数使用new关键字调用,如§8.2.3 所述。使用new调用构造函数会自动创建新对象,因此构造函数本身只需要初始化该新对象的状态。构造函数调用的关键特征是构造函数...
在以往的示例中,每个闭包都有它自己的环境;而这次我们只创建了一个环境,为三个函数所共享:Counter.increment,Counter.decrement 和Counter.value。 该共享环境创建于一个匿名函数体内,该函数一经定义立刻执行。环境中包含两个私有项:名为 privateCounter 的变量和名为 changeBy 的函数。 这两项都无法在匿名函数外部...
number = number + 1; number++; Similar to operator “++”, which increments a number by 1, you can use operator “--" which decrements a number for 1. So, again, both of the following commands do the same thing:Copy number = number - 1; number--; To...
100 / 48 remainder = 4 a++; b--; // postfix increment and decrement Bitwise operators & AND 5 & 1 (0101 & 0001) 1 (1) | OR 5 | 1 (0101 | 0001) 5 (101) ~ NOT ~ 5 (~0101) 10 (1010) ^ XOR 5 ^ 1 (0101 ^ 0001) 4 (100) << left shift 5 << 1 (0101 << 1...
each time we loop, we decrement (reduce scoops by 1), write another string to the browser, and keep going. var scoops = 5; while (scoops > 0) { document.write("Another scoop!"); scoops = scoops - 1; } document.write("Life without ice cream isn't the same"); And continues...
concatenates strings // JavaScript defines some shorthand arithmetic operators let 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...