記一次reduce的使用注意點

當數組等於1時,reduce裏不會打印

var numbers = [{key:15.5}];

function getSum(total, num) {
    console.log('打印')
    return typeof(total) === 'number' ? total + Math.round(num.key):total.key + Math.round(num.key);
}
function myFunction(item) {
    document.getElementById("demo").innerHTML = numbers.reduce(getSum, 0);
}

getSum裏面的 console沒有打印 reduce直接返回numbers 0索引整個元素對象

當數組長度大於1時，reduce裏會打印

var numbers = [{key:15.5}, {key:2.3}, {key:1.1}];

function getSum(total, num) {
    console.log('打印')
    return typeof(total) === 'number' ? total + Math.round(num.key):total.key + Math.round(num.key);
}
function myFunction(item) {
    document.getElementById("demo").innerHTML = numbers.reduce(getSum, 0);
}

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