javascript - 我收到未捕获的 TypeError : Cannot read property 'length' of null on jquery. main.js

Question

这一行:

this.textActive = this.focused || (this.element.value.length && this.element.value !== this.origValue);

正在生成此错误消息:未捕获类型错误:无法读取 null 的属性“长度”

我不确定是什么原因造成的，但它会产生问题。

refreshClasses: function() {
        this.textActive = this.focused || (this.element.value.length && this.element.value !== this.origValue);
        this.setStateClass(this.element, this.options.inputFocusClass,this.focused);
        this.setStateClass(this.elementParent, this.options.parentFocusClass,this.focused);
        this.setStateClass(this.labelFor, this.options.labelFocusClass,this.focused);
        this.setStateClass(this.element, this.options.inputActiveClass, this.textActive);
        this.setStateClass(this.elementParent, this.options.parentActiveClass, this.textActive);
        this.setStateClass(this.labelFor, this.options.labelActiveClass, this.textActive);
    },
    setStateClass: function(el,cls,state) {
        if(!el) return; else if(state) addClass(el,cls); else removeClass(el,cls);
    }
}

Answer 1

在您的代码中，您没有考虑到 value 属性可能未定义，因此不检查长度，而是使用 typeof 检查类型:

this.textActive = this.focused || (typeof this.element.value == 'undefined' && this.element.value !== this.origValue);