javascript - 使用带有 javascript 的逻辑运算符压缩 if/else if 语句

Question

我正在学习 AngularJS，试图制作一个简单的计算器，并且我正在尝试压缩这个 if/else if 语句到 1-2 行，使用 Javascript 逻辑运算符(&&、||、!)

鉴于此示例，我该如何减少它？(不懂$scope的可以无视，基本就是一个 View 。所以当有人点击9时，计算器会在答题屏上显示9)

$scope.setOperand = function (operandEntered) {

    if ($scope.leftOperand === null) {
        $scope.leftOperand = operandEntered;
    } 
    else if ($scope.operator === null) {
        $scope.leftOperand = $scope.leftOperand + operandEntered;
    } 
    else if ($scope.rightOperand === null) {
        $scope.rightOperand = operandEntered;
    } 
    else if ($scope.answer === null) {
        $scope.rightOperand = $scope.rightOperand + operandEntered;
    }
 };

Answer 1

一个人总是可以(尝试)变得聪明，但是当代码变得更长并且不再更可重用时，抽象并不总能带来返回。 KISS .

如果你愿意，我会选择

function addTo(property, x, operand) { // "x" for lack of a more meaningful name
    const shouldAdd = $scope[property] === null || $scope[x] === null;
    if (shouldAdd)
        $scope[property] += operand; // assuming "operand" is a number
// or   $scope[property] = ($scope[property] || "") + operand; // when it's a string
    return shouldAdd;
}
$scope.setOperand = function (operandEntered) {
    addTo("leftOperand", "operator", operandEntered) || addTo("rightOperand", "answer", operandEntered);
 };

如果你更关心简洁而不是可读性，你甚至可以将帮助程序缩短为

function addTo(property, x, operand) {
    return ($scope[property] === null || $scope[x] === null) && (($scope[property] += operand), true);
}