计算数组中每个元素出现的次数 var names = ['Alice', 'Bob', 'Tiff', 'Bruce', 'Alice']; var countedNames = names.reduce(function (allNames, name) { if (name in allNames) { allNames[name]++; } else { allNames[name] = 1; } return allNames; }, {}); // countedNames is: /…