严格比较二叉树，左子树和右子树严格相等：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
function Node(value){
this.value = value;
this.left = null;
this.right = null;
}
var nodeA = new Node("a");
var nodeB = new Node("b");
var nodeC = new Node("c");
var nodeD = new Node("d");
var nodeE = new Node("e");
var nodeF = new Node("f");
var nodeG = new Node("g");
nodeA.left = nodeB;
nodeA.right = nodeC;
nodeB.left = nodeD;
nodeB.right = nodeE;
nodeC.left = nodeF;
nodeC.right = nodeG;
var a = new Node("a");
var b = new Node("b");
var c = new Node("c");
var d = new Node("d");
var e = new Node("e");
var f = new Node("f");
var g = new Node("g");
a.left = b;
a.right = c;
b.left = d;
b.right = e;
c.left = f;
c.right = g;
//严格比较二叉树，左子树和右子树必须完全一样，不可互换
function compareTree(root1, root2){
if(root1 == root2) return true;//两棵树是同一棵树
if((root1 == null && root2 != null) || (root1 != null && root2 == null)) return false;//两棵树有一棵为null，另一棵不是null
if(root1.value != root2.value) return false;//节点的值不同
var leftBoolean = compareTree(root1.left, root2.left);//比较左子树
var rightBoolean = compareTree(root1.right, root2.right);//比较右子树
return leftBoolean && rightBoolean;//左子树和右子树必须都一样
}
console.log(compareTree(nodeA, a));
</script>
</body>
</html>
非严格比较二叉树，左子树和右子树可以互换：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
function Node(value){
this.value = value;
this.left = null;
this.right = null;
}
var nodeA = new Node("a");
var nodeB = new Node("b");
var nodeC = new Node("c");
var nodeD = new Node("d");
var nodeE = new Node("e");
var nodeF = new Node("f");
var nodeG = new Node("g");
nodeA.left = nodeB;
nodeA.right = nodeC;
nodeB.left = nodeD;
nodeB.right = nodeE;
nodeC.left = nodeF;
nodeC.right = nodeG;
var a = new Node("a");
var b = new Node("b");
var c = new Node("c");
var d = new Node("d");
var e = new Node("e");
var f = new Node("f");
var g = new Node("g");
a.right = b;
a.left = c;
b.left = d;
b.right = e;
c.left = f;
c.right = g;
//非严格比较二叉树，左子树和右子树可互换
function compareTree(root1, root2){
if(root1 == root2) return true;//两棵树是同一棵树
if((root1 == null && root2 != null) || (root1 != null && root2 == null)) return false;//两棵树有一棵为null，另一棵不是null
if(root1.value != root2.value) return false;//节点的值不同
return (compareTree(root1.left, root2.left) && compareTree(root1.right, root2.right) || compareTree(root1.right, root2.left) && compareTree(root1.left, root2.right));//左子树和右子树可以互换
}
console.log(compareTree(nodeA, a));
</script>
</body>
</html>