提高具有通用模式的多个 if 语句的可读性

Question

我正在做一些 JavaScript 前端，我有大量的表单，所有这些都需要验证。截至目前，我正在使用这种结构：

function validateForm() {
    let form = document.forms["form-add-consumer"];

    let id = form["input-id"].value;
    let lastName = form["input-last-name"].value;
    let firstName = form["input-first-name"].value;
    ...

    let missing = false;
    if (lastName.trim() === "") {
        document.getElementById("input-last-name-error").className = "error";
        missing = true;
    }
    if (firstName.trim() === "") {
        document.getElementById("input-first-name-error").className = "error";
        missing = true;
    }

    if(missing){
        return false
    } else {
        return buildRequest(id, firstName, lastName, ...);
    }
}

如您所见，对于大型表单，该功能将快速增长。每个字段的代码有点多余：

1. 声明表单域
2. 根据布尔条件检查其值
3. 如果布尔值失败，则显示错误标签并将失败的布尔值设置为 true 以不发送请求

我怎样才能改进这段代码而不使其过于复杂（如果可能，不要使用库）？

Answer 1

也许您可以创建一个包含每个字段验证器的对象，并为各个字段提供选择器，以便您可以以更简洁的方式执行必要的验证，如下所示：

function validateForm() {
    let form = document.forms["form-add-consumer"];

    let id = form["input-id"].value;
    let lastName = form["input-last-name"].value;
    let firstName = form["input-first-name"].value;
    ...

    // Construct an object with selectors for the fields as keys, and 
    // per-field validation functions as values like so
    const fieldsToValidate = {
      '#input-id' : value => value.trim() !== '',
      '#input-last-name' : value => value.trim() !== '',
      '#input-first-name' : value => value.trim() !== '',
      ...,
      '#number-field' : value => parseInt(value) > 0, // Different logic for number field
      ...
    }

    const invalidFields = Object.entries(fieldsToValidate)
    .filter(entry => {

        // Extract field selector and validator for this field
        const fieldSelector = entry[0];
        const fieldValueValidator = entry[1];
        const field = form.querySelector(fieldSelector);

        if(!fieldValueValidator(field.value)) {
            // For invalid field, apply the error class
            field.className = 'error'
            return true;
        }

        return false;
    });

    // If invalid field length is greater than zero, this signifies
    // a form state that failed validation
    if(invalidFields.length > 0){
        return false
    } else {
        return buildRequest(id, firstName, lastName, ...);
    }
}