function formatToStandardizedDate(from, to){

    const from_date = moment(from);

    if(to){
        let to_date = moment(to);
    }else{
        let to_date = null;
    }
}

console.log(formatToStandardizedDate("2017-04-19 00:00:00",null))

What's wrong with my code above? if to is null it at least assign a null to to_date but I got error of to_date of undefined error. Why?

function formatToStandardizedDate(from, to){

    const from_date = moment(from);

    if(to){
        let to_date = moment(to);
    }else{
        let to_date = null;
    }
}

console.log(formatToStandardizedDate("2017-04-19 00:00:00",null))

What's wrong with my code above? if to is null it at least assign a null to to_date but I got error of to_date of undefined error. Why?

• javascript
• reactjs

Share Improve this question Follow asked Apr 12, 2017 at 11:40 Alex YongAlex Yong 7,65588 gold badges2727 silver badges4242 bronze badges 4

• 2 with let you can't use same names of var. – Jai Commented Apr 12, 2017 at 11:42
• 1 Possible duplicate of What's the difference between using "let" and "var" to declare a variable? – mxr7350 Commented Apr 12, 2017 at 11:43
• You'd need to define the let outside of the block if you want to use it outside the block. – Dave Newton Commented Apr 12, 2017 at 11:44
• Where are you using to_date? – Satpal Commented Apr 12, 2017 at 11:44

Add a ment  | 

1 Answer 1

Sorted by: Reset to default 7

You can't use same variable names with let keyword. It will throw errors if you try to do this.

---

Instead you have to use ternary operator:

let to_date = to ? moment(to) : null;

or declare it once above in the function and update the variable

function formatToStandardizedDate(from, to){
    const from_date = moment(from);
    let to_date = null; // initialize the variable with null
    if(to)
      to_date = moment(to); // <---here update the variable with new value.
}

_{Updated as per JaredSmith's ment and that seems good.}