In ESLint mode, for in will report an error when traversing the object, which can be solved as follows:

let  val  = { shu: [ 1 , 2 , 3 ]} ;
for  (let  item  in  val) {
  if  (val.hasOwnProperty(item)) { 
    console.log(item);
  }
}

Because we should judge whether the object has its own properties (non-inheritance) before traversing an object. If the object is an empty object, then there is no need to traverse it to improve the efficiency of the code.

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