In this section, we will learn what the ToString operation is and how to use it in JavaScript.
Note: In this section, we’re assuming you already familiar with the type coercion as well as the ToPrimitive operations.
What is ToString Operation in JavaScript?
When there’s a non-String type value involved in an operation that needs values of type String, the execution engine will run the `ToString` operation on it to coerce that value into a String data type.
The ToString operation is the process of turning a non-string value into string. This operation is different for each datatype, as the list in the table below shows.
Example: running ToString operation in JavaScript
const res = "10" + 10; console.log(res);
Output:
1010
In an addition-operation, when either of operands that are involved in the operation is of type String, the other operand will be coerced into type String as well.
In the statement:
const res = "10" + 10;
The first operand is of type `String`. This means the second operand should be of type string as well. So the execution engine will use the `ToString` operation and coerce the second operand into String data type.
List of Primitive and Object Values and the Result of Applying ToString Operation
In the table below you can see a list of primitive values and the result of applying `ToString` operation on them:
| Primitive value | After ToString operation |
| null | “null” |
| undefined | “undefined” |
| true | “true” |
| false | false |
| 3.14159 | “3.14159” |
| 0 | “0” |
| -0 | “0” |
JavaScript Object to String
Applying the `ToString` operation to values of type object (including arrays) will cause the `toString()` method of that target object to be invoked. Or, to be more specific, the execution engine will run the `ToPrimitive` operation on that object. The details are explained in the ToPrimitive section.
In the table below you can see a list of objects and the result of applying the `ToString` operation on them:
| Object value | After ToString operation |
| {} | “[object Object]” |
| {a:2} | “[object Object]” |
| {toString(){return “John Doe”;}} | “John Doe” |
