Introduction to the problems and differences between apply and Math.max() functions in js

This article mainly introduces the issues of apply and Math.max() functions in js. This article brings you two answers. Each answer is introduced to you in great detail. At the bottom of the article, js is mentioned. Friends who are interested should take a look at the difference between Math.max.apply and Math.max.

The following will introduce to you the problems of apply and Math.max() functions in js. The specific content is as follows:

var arr=[1,3,6,3,7,9,2];
console.log(Math.max.apply(null,arr));

I still don’t understand why the maximum value of an array can be calculated in this way? I still can't figure it out, please give some advice from a js expert.

Answer 1

Function.apply() is an OOP feature of JS. It is generally used to simulate inheritance and extending this. For The above code can be understood like this:

XXX.apply is a method of calling a function, and its parameters are: apply(Function, Args),

Function is the method to be called, Args is the parameter list. When Function is null, the default is as above.
is

Math.max.apply(null, arr)

which can be considered as

apply(Math.max, arr)

Then, arr is a parameter list. For the max method, its parameters are several numbers, that is,

Math.max(a, b, c, d, ...)

When using apply, add all parameters to an array, that is,

arr = [a, b, c, d, ...]

is substituted into the original formula,

Math.max.apply(null, [a, b, c, d, ...])

is actually equivalent to

Math.max(a, b, c, d, ...)

Here, the advantage of using apply is to improve performance in some JS engines.

Answer 2

Math.max() method supports passing multiple parameters, such as: Math.max(1,4,2,3,7,5,6)

But it does not support directly passing an array as a parameter, such as: Math.max(new Array( 1,4,2,3,7,5,6)).

Here, as long as we have a way to split the array one by one and pass it to the Math.max() method, the method of passing the array is implemented.

All functions have the apply (scope chain, parameter) method. The "parameter" of this function receives an array, and separates each value in the array and passes it to the caller

Supplement:

The difference between Math.max.apply and Math.max in Javascript

Javascript The Math.max method in can find the largest number among the given parameters.

> Math.max('1','2','3.1','3.2')
< 3.2
> Math.min(1,0,-1)
< -1

#But if it is an array, it cannot be called like this.

The apply method is used at this time:

apply 方法 (Function) (JavaScript)
调用函数，并用指定对象替换函数的 this 值，同时用指定数组替换函数的参数。
apply([thisObj[,argArray]])
thisObj
　　可选。 要用作 this 对象的对象。
argArray

Optional. A set of arguments to be passed to the function.
Cleverly make the array also call Math.max and Math.min.

> Math.max.apply(null, ['1','2','3.1','3.2'])
< 3.2
> Math.min.apply(null, [1,0,-1])
< -1

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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