ftao/index.html

## index.html
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">

	<style>

	#result{
		width:900px;
		line-height:25px;
	}
	#result ol li {
		width:30%;
		float:left;
	}
	</style>

	<style>
	@media print {
		#control {
			display:none;
		}
		#result {
			margin-top:20px;
			font-size:18px;
		}
	}
	</style>
</head>
<body>
<script>
var operators = ["+", "-", "*", "/"];
var mulOperators = ['*', '/'];

var opMap = {
	'+' : ' + ',
	'-' : ' - ',
	'*' : ' × ',
	'/' : ' ÷ '
};
var minNumber = 1;
var maxNumber = 100;

function translateOp(op){
	return opMap[op];
}

function genNumber(min, max) {
    return Math.floor(Math.random() * (max - min) + min);
}
function genOperator() {
    var index = genNumber(0, 4);
	return operators[index];
}

function isInt(n) {
   return n % 1 === 0;
}

function isResultValidNumber(parts){
	var expr = parts.join("");
	var ret = eval(expr);
	return (ret >= minNumber && ret < maxNumber &&  isInt(ret));
}

function isValidExpr(parts){
	if (mulOperators.indexOf(parts[1]) == -1
	    && mulOperators.indexOf(parts[3]) >= 0){   // first op is not */,  second op is * /
		return isResultValidNumber(parts.slice(2, 5)) && isResultValidNumber(parts);
	}
	else{
		return isResultValidNumber(parts.slice(0, 3)) && isResultValidNumber(parts);
	}
}
function genExpr(){
    while (1){
		var parts = [
			genNumber(minNumber, maxNumber),
			genOperator(),
			genNumber(minNumber, maxNumber),
			genOperator(),
			genNumber(minNumber, maxNumber),
	    ];
	    if(isValidExpr(parts)){
			var expr = parts.join("");
			var ret = eval(expr);
			parts.push(' = ');
			parts.push(ret);
			return parts;
	   }
	}
}

function genPuzzle(){
	var expr = genExpr();
	var location = genNumber(0, 4) * 2;
	expr[location] = '(&nbsp; &nbsp; &nbsp;)';
	expr[1] = opMap[expr[1]];
	expr[3] = opMap[expr[3]];
	return expr.join("");
}

function genPaper(count, targetId){
    var target = document.getElementById(targetId);
	var text = ["<ol>"];
	for(var i = 0; i < count; ++i){
		text.push("<li>" +  genPuzzle() + "</li>");
	}
	text.push("</ol>");
	target.innerHTML = text.join("\n");;
}

function gen(){
	var count = parseInt(document.getElementById('count').value);
	genPaper(count, 'result');
}
</script>
<div id="control">
	题目数量： <input type="text" id="count" value="75" />
	<button onclick="gen();">生成题目</button>
</div>

<div id="result" >

</div>


</body>
</html>
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8">

	<style>

	#result{
	width:900px;
	line-height:25px;
	}
	#result ol li {
	width:30%;
	float:left;
	}
	</style>

	<style>
	@media print {
	#control {
	display:none;
	}
	#result {
	margin-top:20px;
	font-size:18px;
	}
	}
	</style>
	</head>
	<body>
	<script>
	var operators = ["+", "-", "*", "/"];
	var mulOperators = ['*', '/'];

	var opMap = {
	'+' : ' + ',
	'-' : ' - ',
	'*' : ' × ',
	'/' : ' ÷ '
	};
	var minNumber = 1;
	var maxNumber = 100;

	function translateOp(op){
	return opMap[op];
	}

	function genNumber(min, max) {
	return Math.floor(Math.random() * (max - min) + min);
	}
	function genOperator() {
	var index = genNumber(0, 4);
	return operators[index];
	}

	function isInt(n) {
	return n % 1 === 0;
	}

	function isResultValidNumber(parts){
	var expr = parts.join("");
	var ret = eval(expr);
	return (ret >= minNumber && ret < maxNumber && isInt(ret));
	}

	function isValidExpr(parts){
	if (mulOperators.indexOf(parts[1]) == -1
	&& mulOperators.indexOf(parts[3]) >= 0){ // first op is not /, second op is /
	return isResultValidNumber(parts.slice(2, 5)) && isResultValidNumber(parts);
	}
	else{
	return isResultValidNumber(parts.slice(0, 3)) && isResultValidNumber(parts);
	}
	}
	function genExpr(){
	while (1){
	var parts = [
	genNumber(minNumber, maxNumber),
	genOperator(),
	genNumber(minNumber, maxNumber),
	genOperator(),
	genNumber(minNumber, maxNumber),
	];
	if(isValidExpr(parts)){
	var expr = parts.join("");
	var ret = eval(expr);
	parts.push(' = ');
	parts.push(ret);
	return parts;
	}
	}
	}

	function genPuzzle(){
	var expr = genExpr();
	var location = genNumber(0, 4) * 2;
	expr[location] = '(     )';
	expr[1] = opMap[expr[1]];
	expr[3] = opMap[expr[3]];
	return expr.join("");
	}

	function genPaper(count, targetId){
	var target = document.getElementById(targetId);
	var text = ["<ol>"];
	for(var i = 0; i < count; ++i){
	text.push("<li>" + genPuzzle() + "</li>");
	}
	text.push("</ol>");
	target.innerHTML = text.join("\n");;
	}

	function gen(){
	var count = parseInt(document.getElementById('count').value);
	genPaper(count, 'result');
	}
	</script>
	<div id="control">
	题目数量： <input type="text" id="count" value="75" />
	<button onclick="gen();">生成题目</button>
	</div>

	<div id="result" >

	</div>


	</body>
	</html>