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DOM learning - add + - button

2022-04-23 08:25:00 【beinlife】

</td>

function calc(btn){
// Find the next span：
//1、 Look up td
var td=btn.parentNode;// Climb up the tree
//2、 stay td Look under span
var span=td.getElementsByTagName("span")[0];// Climb down the tree
//3、 Take out span Number of numbers n
var num=span.innerHTML;
//4、 If btn yes +, be n++, otherwise n--
btn.innerHTML=="+"?num++:num--;
//5、 If n==0, Is changed to 1
num==0&&(num=1);
//6、 take n Put back span in
span.innerHTML=num;
}