Using jQuery object understanding

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jQuery selector re-use best practice 2 answers

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Second wrapping does nothing as I remember. So if there can be a selector a dom element or a jQuery object you can just wrap it and do not care about what it was.

But if you know it is a jquery object, you shouldn't use wrapping.

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当开发人员开发一个函数时，例如在一个jQuery插件中，它可以获得一个DOM元素或jQuery对象或选择器的参数，然后他们使用它：

function x(container) {
    container = $(container);
    // use container as a jquery object
}

// these both work:
x("#containerId");
x($("#containerId"));
x(document.getElementById("containerId"));

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Case 1: Using a jQuery selector to find a dom element and return a jQuery object:

var container =  $("#containerId");

// Then use it as:
container.hide();

Case 2: Redundant/mistake (or perhaps if you're unsure if a variable is already a jQuery object but you need it to be): Using a jQuery selector to find a dom element and return a jQuery object then pass it to a new jQuery object:

var container =  $("#containerId");

// Then use it as:
$(container).hide();

Case 3: Select a dom element then use it in constructor for a new jQuery object (on which you then call hide() )

var container =  document.getElementById("#containerId");

// Then use it as:
$(container).hide();

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