Javascript for循环和if语句计数器变量范围

Question

function analyse(data) {
    var counter = 0;
    for (let i = 0; i < data.length; i++) {
        if (data[i].closed == true) {
            counter++;
        }
    }
    $scope.totalOpen = data.length - counter;
    $scope.totalClosed = counter;
}

我正在编写一个简单的函数来迭代数组并递增 counter如果数组值内的对象为真。但是，看起来像 counter if 内的变量语句与 counter 的作用域不同for 上方的变量环形。因此，totalClosed即使有一些对象已关闭为 true，变量也只会被赋值为零.我想我没有正确理解 Javascript 中范围界定的概念。有谁能帮帮我吗？

Answer 1

要建立在@Taplar 的旁注上，您可以使用过滤器更干净地实现此目标:

function analyse(data) {
    var closedItems = data.filter(function (item) { return item.closed });
    var totalClosed = closedItems.length;
    var totalOpen = data.length - totalClosed;
    console.log(totalOpen)
    console.log(totalClosed)
}

或者，在 ES6 语法中:

const analyze = (data) => {
    const closedItems = data.filter(item => item.closed);
    const totalClosed = closedItems.length;
    const totalOpen = data.length - totalClosed;
    return {totalOpen, totalClosed}
}