JS计算器无法计算两位数

Question

I made a simple JavaScript calculator and it works when only using single digit numbers. But when you try to use double digit numbers (like 12), it won't work. For instance, 1+2=3 but 1+12=2 because it only calculates the first two numbers entered.

I believe this is because I have an array set up to collect the first 2 numbers pressed, and then to operate on those 2 numbers, as shown in the code below. How can I fix this?

var res = add(operands[0], operands[1]);

My code: http://jsfiddle.net/r8X9N/

Answer 1

The easiest way in my opinion One way would be to keep your operands as strings until you are ready to use them.

http://jsfiddle.net/r8X9N/2/

function subtract(a,b) {
    return parseInt(a,10) - parseInt(b,10);
}


var operands = ["",""];
var operator;

$(".screen").text("");

$(".num").each(function() {
    var selection = $(this).text();
    $(this).click(function() {
        $(".screen").append(selection);
        if (operator) {
            operands[1] = operands[1] + selection;
        } else {
            operands[0] = operands[0] + selection;
        }
    });
});

---

Another option would be to not store the operands at all and instead take the text of the string and eval it (after you get over the fact that you're using eval)

http://jsfiddle.net/r8X9N/3/

$(".screen").text("");

$(".num, .operator").each(function() {
    var selection = $(this).text();
    $(this).click(function() {
        $(".screen").append(selection);
    });
});

$(".equals").click(function() {
    $(".screen").text(function(i,text){
        return eval("(" + text + ")");
    });
});

$(".clear").click(function() {
    $(".screen").text("");
});

The plus side to this version is that it now supports multiple operators and any operator that works in javascript without any additional code (just added an error catch.) http://jsfiddle.net/r8X9N/5/

Answer 2

http://jsfiddle.net/r8X9N/4/

You can also store the numbers pressed in an array, and join them when an operator or equals is pressed.

var num = [];

$(".screen").text("");

$(".num").each(function() {
    var selection = $(this).text();
    $(this).click(function() {
        $(".screen").append(selection);
        num.push(parseInt(selection));
        //operands.push(parseInt(selection));
    });
});

$(".operator").each(function() {
    var selection = $(this).text();
    $(this).click(function() {
        operator = selection;
        operands.push(parseInt(num.join('')));
        num = [];
        $(".screen").append(operator);
    });
});

$(".equals").click(function() {
    operands.push(parseInt(num.join('')));
    num = [];
    switch (operator) {
        case "+":
            var res = add(operands[0], operands[1]);
            $(".screen").text("").append(res);
            operands = [];
            operator = "";