如何避免 javascript 中的代码重复？

Question

I'm writing a node program where I input an id (required) and an attribute (optional) and the function iterates through an array of objects until it finds an object that has the same input id and/or attribute.

So far I have this and it works:

       if(id && query === undefined){
       let searchById = employeesObj.filter(employee => {
           return employee.id == id
       }) 
       if(Object.entries(searchById).length === 0){
           console.log('This employee doesn\'t exist')
           return
    }
    console.log('Employee information: \n', searchById)
    } 

    if(query){
        let searchById = employeesObj.filter(employee => {
            return employee.id == id
        })
        if(Object.entries(searchById).length === 0){
            console.log('This employee doesn\'t exist')
            return}
        let obj = searchById[0]
        if(obj.hasOwnProperty(query)){
            console.log(obj[query])
        }else{
        console.log('input query doesn\'t exist')
    }
    } 

})

As you can see, this part of the functions is the same:

let searchById = employeesObj.filter(employee => {
       return employee.id == id
   }) 
   if(Object.entries(searchById).length === 0){
       console.log('This employee doesn\'t exist')
       return
}

In one it searches when you input an id and in other when you input a query(attribute).

How can I avoid repetition in my code?

Answer 1

In general, if you have to run code more than once, you put it into a function. However, a better way to fix code repetition is to avoid repeating the thing in the first place. You can do that here by doing the ID search at the beginning, only once, and keeping the searchById result around for when you check for the query:

let searchById = employeesObj.filter(employee => {
    return employee.id == id
}) 
if(Object.entries(searchById).length === 0){
    console.log('This employee doesn\'t exist')
    return
}


if(query){
    let obj = searchById[0]
    if(obj.hasOwnProperty(query)){
        console.log(obj[query])
    } else {
        console.log('input query doesn\'t exist')
    }
} else {
    console.log('Employee information: \n', searchById)
}