为什么在 console.log 之后没有调用 Javascript

Question

I am trying to create a function which console.log object or an array type

function whichDataStructure (ITEM){

     if (typeof  ITEM ==='object'){
        console.log ('I am object');
   } if (typeof  ITEM === 'array') {
    console.log ('i am array');

   } else {
    console.log(' neither');


  }
};

Answer 1

In Javascript Arrays are actually a kind of Object.

You have to use the Array.isArray() function to find out if a value is an Array:

function whichDataStructure(item) {
    if (Array.isArray(item)) {
        console.log('I am an Array');
    } else if (typeof item === 'object'){
        console.log('I am an Object');
    } else {
        console.log('I am of type: ' + typeof item);
    }
};

It is important that you test if the value is an Array before testing if it is an Object. Otherwise it will always be seen as an Object.