Question

我想要做的是在HTMLInputElement上触发onchange事件后获取新值。我知道我可以通过使用element.value来获得它，但是这不会在大局中起作用。请参阅以下代码：

//This Works:
     elem.onchange = (ev: Event) => {
                    var newValue = (<HTMLInputElement>ev.srcElement).value; 
                    alert("Old: " + this._data[key] + ", New: " + newValue);
}

//Is there anyway I can get it to work like below? Currently I keep getting old values as new and old.
     elem.onchange = (ev: Event) => {
                    var attName = "checked"; //or "value"  for example
                    var newValue = ev.srcElement.getAttribute(attName); 
                    alert("Old: " + this._data[key] + ", New: " + newValue);
}

Answer 1

您无法使用getAttribute("checked")来判断是否选中了复选框。您需要使用checked属性：

elem.onchange = function (ev) {
    var element = <HTMLInputElement>ev.srcElement,
        newValue: string | boolean;

    if (element.type === "checkbox") {
        newValue = element.checked;
    }
    else {
        newValue = element.value;
    }

    alert("Old: " + this._data[key] + ", New: " + newValue);
};

TypeScript（JS） - 从onchange函数获取更改的值

1 个答案: