Several parameter forms in JS functions

A function is a piece of code that is combined to perform a specific task. Functions generally use parameters to interact with the outside world. To write concise and efficient JS code, you must master function parameters.
In this article, some interesting examples will be used to explain all the features that JS has to handle function parameters efficiently.

1. Function parameters

function sum(param1, param2) 
{    
    console.log(param1); // 1
    console.log(param2); // undefinedreturn 
    param1 + param2;
 }
 sum(1); // NaN

The number of parameters passed in during the call should be the same as the number of parameters defined in the function. Of course, the number of parameters passed in is less than the number of parameters defined in the function. Sometimes, no error will be reported, and undefined will be used instead.

2. Default parameters

function sum(param1, param2 = 0) 
{   
 console.log(param2); //  0
 return param1 + param2;
 }
 sum(1);            // 1
 sum(1, undefined); // 1

If the second parameter is not passed in, param2 will default to 0.
Note that if undefined is set to the second parameter sum(1, undefined), param2 will also be initialized to 0.

3. Destructuring parameters

functiongreet({ name }) 
{  
    return`Hello, ${name}!`;
}
const person = { name: '前端' };
greet(person); // 'Hello, 前端'

4. arguments object

JavaScript function has a built-in object arguments object. The argument object contains the argument array for the function call. In this way you can easily find the largest parameter value

x = findMax(1, 123, 500, 115, 44, 88); 
function findMax() {
    var i, max = arguments[0];    
    if(arguments.length < 2) return max; 
    for (i = 0; i < arguments.length; i++) {
        if (arguments[i] > max) {
            max = arguments[i];        }
    }
    return max;}

5. The remaining parameters

will be an indefinite number of The parameters are represented as an array

function sumArgs() {
  console.log(arguments); // { 0: 5, 1: 6, length: 2 }
  let sum = 0;
  for (let i = 0; i < arguments.length; i++) {
    sum += arguments[i];
  }
  return sum;
}

sumArgs(5, 6); // => 11

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