Refactor: Replace jQuery utilities with ES6+ alternatives

[wenzhixin]

🤔 Type of Request

• Bug fix
• New feature
• Improvement
• Documentation
• Other

📝 Description

This PR refactors the codebase to replace jQuery utility methods with modern ES6+ alternatives. The code is now more idiomatic and aligns with modern JavaScript best practices.

🎯 Changes

1. Replace $.extend() with native extend()

• Uses a proven implementation from bootstrap-table
• Supports both shallow merging: extend({}, obj1, obj2)
• And deep merging: extend(true, {}, obj)
• Maintains full API compatibility with jQuery's extend

2. Replace $.each() with native for...of

• Before: $.each(collection, (i, elm) => { ... })
• After: for (const [i, elm] of Array.from(collection).entries()) { ... }
• More idiomatic ES6+ syntax

3. Replace $.inArray() with native Array.prototype.includes()

• Before: if ($.inArray(option, Constants.METHODS) < 0)
• After: if (!Constants.METHODS.includes(option))
• Simpler and more readable

📁 Files Modified

• src/MultipleSelect.js - Updated to use extend() and for...of
• src/multiple-select.js - Updated to use extend() and includes()
• src/utils/index.js - Added extend() and isObject() utilities

✨ Benefits

• More native: Uses ES6+ features instead of jQuery utilities
• More maintainable: Less dependency on jQuery's internal API
• Better performance: Native methods are generally faster
• Cleaner code: includes() is more intuitive than inArray()
• Future-proof: Ready for jQuery 4.0+ where some utilities are deprecated

✅ Testing

All existing functionality is preserved. No breaking changes for end users.

🔍 Code Examples

// Before
$.extend({}, Constants.DEFAULTS, options)
$.each(this.$el.children(), (i, elm) => { ... })
if ($.inArray(option, Constants.METHODS) < 0) { ... }

// After
extend({}, Constants.DEFAULTS, options)
for (const [i, elm] of Array.from(this.$el.children()).entries()) { ... }
if (!Constants.METHODS.includes(option)) { ... }

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[Copilot]

Pull request overview

This PR refactors the multiple-select plugin to reduce reliance on jQuery utility helpers by introducing a native extend() utility and replacing $.each / $.inArray usage with ES6+ equivalents.

Changes:

• Added extend() (and internal plain-object detection) to src/utils/index.js and exported it for reuse.
• Replaced $.extend() usages with extend() in core initialization and option-handling paths.
• Replaced $.each() loops with for...of iteration and replaced $.inArray() checks with Array.prototype.includes().

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/utils/index.js	Introduces and exports a native extend() implementation to replace $.extend().
src/multiple-select.js	Updates plugin entrypoint to use extend() and includes() for method validation.
src/MultipleSelect.js	Updates core class to use extend() and replaces $.each() loops with for...of.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 7 changed files in this pull request and generated 1 comment.

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