<!doctype html>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>20以内加减法</title>
<head>
<meta charset="utf-8">
<script>
var count = 0;
var con;
function getRandom(num1) {
return Math.floor(Math.random()*num1);
}
function getOperator() {
var arr = ['+', '-', '×', '÷'];
arr = ['+', '-'];
return arr[Math.floor(Math.random()*arr.length)];
}
function validate(num1, op, num2) {
if (op === '÷' && num2 === 0) return false;
if (num1%num2 != 0) return false;
if (op === '-' && num1 < num2) return false;
return true;
}
function create() {
con = document.getElementById("content");
var num1 =