What is the usage of adding an empty string in a javascript statement - Stack Overflow

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I see an empty string ('' or "") used in many JavaScript statements but not sure what does it stand for.

e.g. var field = current.condition_field + '';

Can someone please clarify?

I see an empty string ('' or "") used in many JavaScript statements but not sure what does it stand for.

e.g. var field = current.condition_field + '';

Can someone please clarify?

• javascript
• string
• concatenation

Share Improve this question Follow edited Jun 23, 2015 at 2:47 Tushar 87.3k2121 gold badges163163 silver badges181181 bronze badges asked Jun 22, 2015 at 13:15 user1934643user1934643 16122 silver badges1111 bronze badges 1

• 5 Number to String; (""+5) + 1 == 51 – Alex K. Commented Jun 22, 2015 at 13:17

Add a ment  | 

1 Answer 1

Sorted by: Reset to default 13

Type Casting. It converts the type to string

If variable current.condition_field is not of string type, by adding '' using + operator at the end/beginning of it converts it to string.

var field = current.condition_field + ''; 

So, field is always string.

Example

var bool = true; // Boolean
var str = bool + ''; // "true"

document.write('bool: ' + typeof bool + '<br />str: ' + typeof str);


var num = 10; // Numeric
var str = num + ""; // "10"

document.write('<br /><br />num: ' + typeof num + '<br />str: ' + typeof str);

Thanks to @KJPrice:

This is especially useful when you want to call a string method(Method defined on string prototype) on that variable.

(myVar + '').toLowerCase();

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