--- schema_version: "1" id: e599401874b8baed9948a393787f0ace1d37a1aab404df9a0e60bea95c8ed923 title: Flow Control and Scope Operations in DataWeave collection: mulesoft version: current locale: en-us portal_url: https://docs.salesforce.com/mulesoft/current/en-us/dataweave/2.6/dataweave-flow-control.md canonical_url: https://docs.mulesoft.com/dataweave/2.6/dataweave-flow-control source_site: docs.mulesoft.com content_type: documentation content_hash: 0e8df4d9a4cd0a0ca125e0b93b15213c62a6e5257f81da7a3ab1c1905782bca2 description: MuleSoft Documentation Site release: "2.6" latest: false --- --- product: DataWeave version: 2.6 --- # Flow Control and Scope Operations in DataWeave > For the full documentation index, see: https://docs.mulesoft.com/llms.txt You can use the following operators within any DataWeave expression: - [`do`](#control_flow_do) - [`if else`](#control_flow_if_else) - [`else if`](#control_flow_else_if) ## `do` A `do` statement creates a scope in which new variables, functions, annotations, or namespaces can be declared and used. The syntax is similar to a mapping in that it is composed of a header and body separated by `---`. Its header is where all the declarations are defined, and its body is the result of the expression. This example uses `do` to return the string `"DataWeave"` when `myfun()` is called from the main body of the script. DataWeave Script: ```dataweave %dw 2.0 output application/json fun myfun() = do { var name = "DataWeave" --- name } --- { result: myfun() } ``` This example uses `do` to return the string `"DataWeave"` when the variable `myVar` is referenced from the main body of the script. DataWeave Script: ```dataweave %dw 2.0 output application/json var myVar = do { var name = "DataWeave" --- name } --- { result: myVar } ``` Both scripts produce this output: Output: ```json { "result": "DataWeave" } ``` The next example uses `do` to prepend the string `"Foo"` to a string (`" Bar"`) that is passed to the `test(p: String)` function. DataWeave Script: ```dataweave %dw 2.0 output application/json fun test(p: String) = do { var a = "Foo" ++ p --- a } --- { result: test(" Bar") } ``` Output: ```json { "result": "Foo Bar" } ``` See also, [Examples: Local DataWeave Variables](https://docs.mulesoft.com/dataweave/2.6/dataweave-variables#example_local_variable). ## `if else` An `if` statement evaluates a conditional expression and returns the value under the `if` only if the conditional expression returns `true`. Otherwise, it returns the expression under `else`. Every `if` expression must have a matching `else` expression. The following example uses the input `{ country : "FRANCE" }`, which is defined by the `myVar` variable in the header: DataWeave Script: ```dataweave %dw 2.0 var myVar = { country : "FRANCE" } output application/json --- if (myVar.country == "USA") { currency: "USD" } else { currency: "EUR" } ``` Output: { "currency": "EUR" } You can use the if-else construct on any condition that evaluates to `true` or `false`, including mathematical, logical, equality, and relational statements. The condition can act on any valid input. The next DataWeave script applies `if else` statements to the result of the following conditional statements: - A mathematical operation in `ex1` The `if else` statement returns the Boolean value `true` if the operation `1 + 1 == 55` is true and `false` if not. - An equality operation in `ex2` The `if else` statement returns `1` if the value of the specified index is `1` or a string if the value is not `1`. - An `isEmpty` function in `ex3` The `if else` statement returns the string `"ID is empty"` or `"ID is not empty"` depending on whether `aRecord.bookId` contains a value. - A mapping in `ex4` that iterates over `firstInput` The `if else` statement returns the value of the `bookId` as a Number if the value is equal to `101`. It returns the specified string if the value is not equal to `101`. DataWeave Script: ```dataweave %dw 2.0 var aRecord = [ "bookId":"101", "title":"world history", "price":"19.99" ] output application/xml --- { examples: { ex1 : if (1 + 1 == 55) true else false, ex2 : if ([1,2,3,4][1] == 1) 1 else "value of index 1 is not 1", ex3 : if (isEmpty(aRecord.bookId)) "ID is empty" else "ID is not empty", ex4 : aRecord.bookId map (idValue) -> if (idValue as Number == 101) idValue as Number else "not 101" } } ``` Output: false value of index 1 is not 1 ID is not empty 101 Additional examples are available in [DataWeave Operators](https://docs.mulesoft.com/dataweave/2.6/dw-operators). ## `else if` You can chain several `else` expressions together within an if-else construct by incorporating `else if`. The following example uses the input `var myVar = { country : "UK" }`, which is defined by the `myVar` variable in the header. DataWeave Script: ```dataweave %dw 2.0 var myVar = { country : "UK" } output application/json --- if (myVar.country =="USA") { currency: "USD" } else if (myVar.country =="UK") { currency: "GBP" } else { currency: "EUR" } ``` Output { "currency": "GBP" } The following example is similar but takes an array as input instead of an object. The body of the script uses `if else` and `else if` statements within a `do` operation to populate the value of the `hello` variable. DataWeave Script: ```dataweave %dw 2.0 output application/json --- ["Argentina", "USA", "Brazil"] map (country) -> do { var hello = if(country == "Argentina") "Hola" else if(country == "USA") "Hello" else if(country == "Brazil") "Ola" else "Sorry! We don't know $(country)'s language." --- "$(hello) DataWeave" } ``` Output: \[ "Hola DataWeave", "Hello DataWeave", "Ola DataWeave" \] ## See Also - [DataWeave Types](https://docs.mulesoft.com/dataweave/2.6/dataweave-types) - [DataWeave Selectors](https://docs.mulesoft.com/dataweave/2.6/dataweave-selectors)