Laravel中引入node_modules的jquery-validation出现validate不是函数问题

Let's break down why you're seeing the "validate is not a function" error even though you've installed and required the jquery-validation package:

The Core Issue #

jQuery plugins like jquery-validation rely on jQuery being available in the global scope (i.e., window.jQuery or window.$) to register their methods (like .validate()) onto jQuery's prototype.

When you use a CDN:

The CDN-hosted jQuery script exposes jQuery and $ globally, so when the CDN-hosted jquery-validation loads, it immediately finds the global jQuery instance and attaches the validate method to it.

But when using require():

• If you don't explicitly expose jQuery to the global window, the jquery-validation module can't find the jQuery instance to attach its methods to. Even if npm installed jQuery as a dependency of jquery-validation, it's loaded as a local module, not a global variable.
• Your current code doesn't include a line to require and expose jQuery globally—you're only requiring jquery-validation, which isn't enough.

Fixes to Try #

1. Explicitly Expose jQuery Globally Before Requiring jquery-validation #

First, make sure jQuery is installed (it should be a dependency of jquery-validation, but double-check with npm install jquery --save if needed). Then update your code to:

// First, expose jQuery to the global window
window.$ = window.jQuery = require('jquery');
// Now load jquery-validation—it will find the global jQuery
window.jqueryvalidation = require('jquery-validation');

// Rest of your code...
window.Vue = require('vue');
window.axios = require('axios');
window.axios.defaults.headers.common['X-Requested-With'] = 'XMLHttpRequest';

Vue.component('error-message', require('./components/Flash_Error_Message.vue'));
Vue.component('like', require('./components/Like.vue'));

const app = new Vue({ el: '#app' });

$(function(){
  $('#postForm').validate({
    // ... your validation rules and callbacks
  });
})

2. Use Webpack's ProvidePlugin (If Using Webpack) #

If your project uses Webpack, you can configure it to automatically provide jQuery globally to all modules, so you don't need to manually assign it to window:

Add this to your webpack.config.js:

const webpack = require('webpack');

module.exports = {
  // ... other configuration settings
  plugins: [
    new webpack.ProvidePlugin({
      $: 'jquery',
      jQuery: 'jquery'
    })
  ]
};

With this setup, you can keep your original require('jquery-validation') line, as Webpack ensures jQuery is available globally for the plugin to use.

Why This Works #

By making jQuery available globally before loading jquery-validation, the plugin can attach its validate method to jQuery.fn (the jQuery prototype), which makes .validate() available on all jQuery objects like $('#postForm').

内容的提问来源于stack exchange，提问作者Theodore