如何 curry jQuery 方法——哪个`this`值将传递 jQuery 对象？

Posted 2023-02-21

【中文标题】如何 curry jQuery 方法——哪个`this`值将传递 jQuery 对象？

【英文标题】：How to curry jQuery methods -- which `this` value will pass the jQuery object?

【发布时间】：2016-04-29 23:35:59

【问题描述】：

如果我想使用 Function.prototype.bind 创建一个 jQuery 函数，即需要一个包装函数，我应该提供哪个 this 值？以下简单示例似乎不起作用：

// e.g.: $.fn.outerHeight() with argument true gets height including margin

$.fn.marginBoxHeight = $.fn.outerHeight.bind($.fn, true);

$.fn 是 this 参数的错误选择。它应该是什么，以便函数可以访问 jQuery 内部方法（如果需要）？

【问题讨论】：

javascriptissexy.com/…

通常在 jQuery 中你不引用或咖喱，你做的更像是$.fn.marginBoxHeight = function() return this.outerHeight(true);

谢谢@adeneo 是的，我知道，事实上我就是这样解决问题的——这更像是一个学术问题。我将不得不查看源代码；我猜正确的范围可能是 $.fn.init 或 $.fn.init.prototype

@lunelson 在这种情况下，学术上的答案可能是“放弃 jQuery，越快越好”。

不可能：this 应该是您调用marginBoxHeight 的对象，您事先并不知道。所以，你不能使用bind。

【参考方案1】：

jQuery.proxy 执行柯里化如下：

QUnit.test( "jQuery.proxy", function( assert ) 

    var thisObject =  foo: "bar", method: test ;

    // jQuery 1.9 improved currying with `this` object context
    fn = function() 
        assert.equal( Array.prototype.join.call( arguments, "," ), "arg1,arg2,arg3", "args passed" );
        assert.equal( this.foo, "bar", "this-object passed" );
    ;
    cb = jQuery.proxy( fn, null, "arg1", "arg2" );
    cb.call( thisObject, "arg3" );
 );

QUnit.test( "jQuery.proxy", function( assert ) 
	assert.expect( 9 );

	var test2, test3, test4, fn, cb,
		test = function() 
			assert.equal( this, thisObject, "Make sure that scope is set properly." );
		,
		thisObject =  foo: "bar", method: test ;

	// Make sure normal works
	test.call( thisObject );

	// Basic scoping
	jQuery.proxy( test, thisObject )();

	// Another take on it
	jQuery.proxy( thisObject, "method" )();

	// Make sure it doesn't freak out
	assert.equal( jQuery.proxy( null, thisObject ), undefined, "Make sure no function was returned." );

	// Partial application
	test2 = function( a ) 
		assert.equal( a, "pre-applied", "Ensure arguments can be pre-applied." );
	;
	jQuery.proxy( test2, null, "pre-applied" )();

	// Partial application w/ normal arguments
	test3 = function( a, b ) 
		assert.equal( b, "normal", "Ensure arguments can be pre-applied and passed as usual." );
	;
	jQuery.proxy( test3, null, "pre-applied" )( "normal" );

	// Test old syntax
	test4 =  "meth": function( a ) 
		assert.equal( a, "boom", "Ensure old syntax works." );
	 ;
	jQuery.proxy( test4, "meth" )( "boom" );

	// jQuery 1.9 improved currying with `this` object
	fn = function() 
		assert.equal( Array.prototype.join.call( arguments, "," ), "arg1,arg2,arg3", "args passed" );
		assert.equal( this.foo, "bar", "this-object passed" );
	;
	cb = jQuery.proxy( fn, null, "arg1", "arg2" );
	cb.call( thisObject, "arg3" );
 );

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://code.jquery.com/qunit/qunit-2.4.0.css">
<script src="https://code.jquery.com/qunit/qunit-2.4.0.js"></script>
<div id="qunit"></div>
<div id="qunit-fixture"></div>

最简单的例子是：

var foo = jQuery.proxy(function()return this('html:first'), jQuery)
console.log(foo() )

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

参考文献

jQuery.proxy() | jQuery API Documentation

jquery/core.js at master · jquery/jquery

jQuery Combinators by raganwald

Combinator Recipes for Working With Objects in JavaScript

Ingredients of Effective Functional JavaScript: Closures, Partial Application and Currying

Partial function application for humans | Andrew Berls

Practical Applications of Partial Application