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The bind method in javascript is used to create a new function, which uses the syntax "function.bind (thisArg [, arg1 [, arg2 [,...]), where the parameter thisArg represents the value passed to the target function as a this parameter when the bound function is called.

This article operating environment: windows7 system, javascript1.8.5 version, Dell G3 computer.

What is the use of bind in javascript?

Function.prototype.bind ()

The bind () method creates a new function, and when bind () is called, the this of the new function is specified as the first argument to bind (), and the remaining parameters are used as arguments to the new function for use when called.

Grammar

Function.bind (thisArg [, arg1 [, arg2 [,...])

Parameter thisArg:

The value passed to the target function as a this parameter when the binding function is called. If the binding function is constructed using the new operator, this value is ignored. When you use bind to create a function in setTimeout (provided as a callback), any raw values passed as thisArg are converted to object. If the argument list of the bind function is empty, or if the thisArg is null or undefined, the this of the execution scope is considered the thisArg of the new function.

Parameters arg1, arg2,...:

A parameter that is preset into the parameter list of the binding function when the target function is called.

Return value:

Returns a copy of the original function with the specified this value and initial parameters.

Description:

The bind () function creates a new binding function (bound function,BF). A binding function is an exotic function object (a term in ECMAScript 2015) that wraps the original function object. Calling a bound function usually results in the execution of the wrapper function.

The binding function has the following internal properties:

[[BoundTargetFunction]]-wrapped function object

[[BoundThis]]-the value that is always passed as the this value when the wrapper function is called.

[[BoundArguments]]-list, any call to the wrapper function fills the parameter list with list elements first.

[[Call]]-executes the code associated with this object. Called through a function call expression. The arguments to the internal method are a th value and a list of parameters passed to the function through the calling expression.

When the binding function is called, it calls the internal method [[Call]] on [[BoundTargetFunction]], like this Call (boundThis, args). Where boundThis is [[BoundThis]] and args is [[BoundArguments]] plus a list of parameters passed in through a function call.

The binding function can also be constructed using the new operator, which behaves as if the target function has been built. The supplied this value is ignored, but the prefix is still provided to the mock function.

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