表达式&&表达式语法是什么意思？

Question

这条线parent && (this.parent.next = this);是什么意思？它只是看起来像坐在那里,什么也不做,不是if声明或承诺或任何东西.这种编码风格有名称吗？

    var Particle = function(i, parent)
{
    this.next = null;
    this.parent = parent;
    parent && (this.parent.next = this);
    this.img = new Image();
    this.img.src = "http://www.dhteumeuleu.com/images/cloud_01.gif";
    this.speed = speed / this.radius;
}

它在我正在看的动画文件的多个地方.这是另一个例子..(!touch && document.setCapture) && document.setCapture();

this.down = function(e, touch)
{
    e.preventDefault();
    var pointer = touch ? e.touches[0] : e;
    (!touch && document.setCapture) && document.setCapture();
    this.pointer.x = pointer.clientX;
    this.pointer.y = pointer.clientY;
    this.pointer.isDown = true;

Answer 1

这是简写

if (parent) {
    this.parent.next = this
}

Answer 2

如果parent为false则不弹出(this.parent.next = this),例如:

parent = false;
parent && alert("not run");

短路评估:

逻辑表达式从左到右进行评估,被称为"短路"评估,

variable && (anything); // anything is evaluated if variable = true.
variable || (anything); // anything is evaluated if variable = false

它可以用于变量的赋值:

var name = nametemp || "John Doe"; // assignment defaults if nametemp is false
var name = isValid(person) && person.getName(); //assignement if person is valid