我有一个函数将来自 AJAX 请求的结果连接在一起。
出于某种原因，我的最后一个字符串以“undefined”开头。
这是一个重现问题的简化示例：
// In practice, fetched via AJAX from a server
var vendors = [{ id_vendor: 'V0001' }, { id_vendor: 'V0002' }];
var row_vendor;
vendors.forEach(function (value) {
row_vendor += value.id_vendor;
});
alert(row_vendor); // undefinedV0001V0002为什么警报值显示前导“未定义”？
我有两个简单的数组:
var arr_must_exist = ["1","2","3"];
var arr_created = ["2","4","7","8"]; //This is varies depend of the array created.
所以,如果arr_created像示例那样应该有一个警告Your choice must contain 1 and 3
例:
arr_created = ["2","4","7","8"];
alert(`Your choice must contain 1 and 3`)
arr_created = ["2","3","7","8"];
alert(`Your choice must contain 1`)
arr_created = ["4","5","7","8"];
alert(`Your choice must contain 1, 2 and 3`)
arr_created = ["1","2","9","3"];
alert(`Your choice is valid`)
我用,$.each但它只检查数组.不比较它们.
$.each(arr_is_must_exist , function(index, val_must_exist) {
$.each(arr_is_exist_in_table , function(index, val_is_exist) {
if(val_must_exist != val_is_exist){ …我有这样一张桌子:
ID Item Total
P-001 ATK001 1500
P-002 ATK001 1750
P-002 ATK002 1250
P-003 ATK001 175
P-003 ATK002 350
P-003 ATK003 400
P-003 CTK001 750
P-003 CTK002 750
P-005 ATK004 500
P-005 ATK117 475
P-005 CTK009 1200
P-005 ATK001 400
P-005 ATK002 125
我想根据'Item'列总结'Total'列.我创建了一些mysql查询,输出如下:
P-001 ATK001 3825
P-002 ATK002 1725
P-003 ATK003 400
P-005 ATK004 500
P-005 ATK117 475
P-003 CTK001 750
P-003 CTK002 750
P-005 CTK009 1200
我想要的输出是:
ID Item Total
P-001 ATK001 3825
P-002 ATK001 3825
P-002 ATK002 …