js判断是由含有a节点_怎么判断某个dom节点是否包含某个dom节点?

var a = document.querySelector('.first-child');

var b = document.querySelector('.second-child-child');

var c = document.querySelector('.first');

var d = document.querySelector('.second');

function isChildOf(child, parent) {

var parentNode;

if(child && parent) {

parentNode = child.parentNode;

while(parentNode) {

if(parent === parentNode) {

return true;

}

parentNode = parentNode.parentNode;

}

}

return false;

}

console.log(isChildOf(a, b));

console.log(isChildOf(b, d));

console.log(isChildOf(a, c));