계산기 (3)
<!doctype html>
<html>
<body>
<script>
var expression = prompt('계산식을 입력해 주세요');
var cursor = 0;
var lastCursorPosition = 0;
var tokens = [];
function supportOperator(op){
return(op == '+' || op == '-')
}
function isOperator(value){
return supportOperator(value);
}
while(cursor < expression.length){
if(isOperator(expression[cursor])){
tokens.push(Number(expression.slice(lastCursorPosition, cursor)));
tokens.push(expression[cursor]);
lastCursorPosition = cursor + 1;
}
cursor = cursor + 1;
}
tokens.push(Number(expression.slice(lastCursorPosition, cursor)));
tokens.push('+'); // Fake operator
var index = 0;
var sum = 0;
var operator = '+';
while(index < tokens.length){
if(isOperator(tokens[index])){
if(operator != ''){
if(operator == '+'){
sum = sum + tokens[index-1];
}else {
sum = sum - tokens[index-1];
}
}
operator = tokens[index];
}
index = index + 1;
}
console.log(sum);
</script>
</body>
</html>
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