Expression Language Examples

This reference provides practical examples of using the expression language in common scenarios. These examples demonstrate real-world use cases for data transformation, validation, filtering, and formatting in SnapLogic pipelines.

Object Examples

Conditional Expression (If-Then-Else):


Expression	`$.hasOwnProperty('query.fred') ? $query.fred : 'not present in input'`
Description	This example demonstrates an if-then-else expression pattern.
Use Case	To set a default pipeline variable in a document object, use this expression for a mapper variable `$lastname`: `$.hasOwnProperty('lastname') ? $lastname : _lastname` `$lastname` has the value of `$lastname` as supplied by a document in the stream. If there is no document input, then `$lastname` is set to the `_lastname` parameter value.

String Examples

Checking for a Non-empty String:


Expression	`$customer.lastname.trim() \|\| 'default'`
Description	The expression verifies if `$customer.lastname` and `$customer.lastname.trim()` has a value. If it does, then the value of `$customer.lastname.trim()` is applied to the target path; otherwise, 'default' gets applied to the target path.

Checking for an Existing Value:


Expression	`$.hasOwnProperty('customer.lastname') \|\| 'default'`
Description	The expression verifies if `$customer.lastname` exists in the input document. It returns `True` if `$customer.lastname` exists, else it shows 'default' as a string and applies it to the target path.

Checking for a Non-empty String AND an Existing Value:


Expression	`($.hasOwnProperty('customer.lastname') && $customer.lastname.trim()) \|\| 'default'`
Description	The expression verifies if a property exists in the input document and if `$customer.lastname` and `$customer.lastname.trim()` provide a value. If it does, then it applies its value to the target path; otherwise, it applies 'default' to the target path.

Creating an Email Address from First Initial and Last Name:


Expression	`$first_name.substr(0,1).toLowerCase() + $last_name.toLowerCase() + "@example.com"` OR `$first_name.charAt(0).toLowerCase() + $last_name.toLowerCase() + "@example.com"`
Description	Either expression grabs the first letter of the `$first_name` field, converts it to lowercase, then adds it to the `$last_name` value and appends "@example.com" before writing it to `$Email`.
Example Result	Where `$first_name` = "John" and `$last_name` = "Doe" Result: "[email protected]"

Date Examples

Creating and Formatting a Date in a Specific Timezone:


Expression	`Date.now().toLocaleDateString('{\"timeZone\":\"PST\", \"format\":\"yyyy-MM-dd\"}')`
Description	The expression creates the current date time in the PST timezone and formats its output into a string in the form of yyyy-MM-dd.

Formatting a Date to Include Letters:


Expression	`Date.now().toLocaleDateTimeString('{\"format\":\"yyyy-MM-dd\'T\'hh:mm:ss.SSS\'Z\'\"}')`
Description	The expression creates the current date time and formats its output into a string to include the letter "T" and "Z". Characters outside of normal SQLDate specials can be added by escaping them.
Example Result	2017-03-15T10:30:45.123Z

Creating an ISO-formatted Date in the Current Timezone:


Expression	`Date.now().toLocaleDateString('{\"timeZone\":\"PST\"}')`
Description	The expression creates the current date time in the local time zone and formats its output into a string for the ISO date time format.

Parsing a Date:


Expression	`Date.parse($StandardDate)`
Description	This expression parses a string representation of `$StandardDate` into a DateTime object. The string representation should have one of the following formats: yyyy/MM/dd yyyy/MM/dd HH:mm yyyy/MM/dd HH:mm:ss yyyy/MM/dd HH:mm:ss.SSS MM/dd/yyyy MM/dd/yyyy HH:mm MM/dd/yyyy HH:mm:ss MM/dd/yyyy HH:mm:ss.SSS MMM dd, yyyy EEE, dd MMM yyyy HH:mm:ss EEE, dd MMM yyyy HH:mm:ss z (where z refers to the general time zone, e.g., GMT-0800 for PST) EEE, dd MMM yyyy HH:mm:ss 'GMT'Z (where Z refers to the GMT time offset, e.g., GMT-0700 for PDT) yyyy-MM-dd yyyy-MM-dd'T'HH:mm:ss yyyy-MM-dd'T'HH:mm:ssXXX yyyy-MM-dd'T'HH:mm:ss.SSS yyyy-MM-dd'T'HH:mm:ss.SSSXXX yyyy-MM-dd HH:mm yyyy-MM-dd HH:mm:ss yyyy-MM-dd HH:mm:ssXXX yyyy-MM-dd HH:mm:ss.SSS yyyy-MM-dd HH:mm:ss.SSSXXX

Parsing a Non-standard Date:


Expression	`Date.parse($NonStandardDate, "yyyy MM dd")` OR `Date.parse($nonstandard_datetime, "yyyy-MM-dd HH:mm:ss.SSS")`
Description	These examples parse the date into a DateTime object using the provided format.

Formatting Today's Date to Display as the Current Month:


Expression	`Date.now().toLocaleDateString({"format":"MMMM"})`
Description	This expression takes today's date and formats the output in a string indicating the month in text.
Example Result	"March"

Filtering Examples

Filtering for Two Possible Values:


Expression	`$Priority == "Resolve Immediately" \|\| $Priority == "High Attention"`
Description	Used in a Filter Snap, this expression finds only those items that have `$Priority` set to either "Resolve Immediately" or "High Attention".

Filtering by Multiple Fields:


Expression	`$Workflow == "Ready For Testing" && (($Priority == "Resolve Immediately") \|\| ($Priority == "High Attention"))`
Description	Used in a Filter Snap, this expression finds only those items that are in the `$Workflow` step of "Ready for Testing" and `$Priority` is set to either "Resolve Immediately" or "High Attention".

Filtering by Date within Timeframe:


Expression	`$ClosedDate >= Date.now().minusHours(24)`
Description	Used in a Filter Snap, this expression finds only those items that have a `$CloseDate` within the last 24 hours.

Other Transformation Examples

Making a Field Value a Link:


Expression	`'<a href="' + $Link + '">' + $ID + '</a>'`
Description	This expression turns the value of the `$ID` field into an HTML link pointing to the location found in the `$Link` field.
Example Result	Where `$ID` = "12345" and `$Link` = "http://example.com" Result: <a href="http://example.com">12345</a>

Mapping Values to an Array:

This series of expressions maps data from:

[
  {
    "ORG_ASSIGNMENT": [
      {
        "ORGTXT": "Network Services",
        "JOBTXT": "Service technician",
        "POSTXT": "Manager"
      }
    ]
  }
]

To name/value pairs within an array:

[
  "Organization": {
    "Unit": [
      [
        "Position",
        "Manager"
      ],
      [
        "Grade",
        "Service technician"
      ],
      [
        "Division",
        "Network Services"
      ]
    ]
  }
]


Expression 1	`['Position', jsonPath($, "ORG_ASSIGNMENT[*].POSTXT").toString()]`
Target Path 1	$Users.User[*].Organization.Unit[0]
Expression 2	`['Grade', jsonPath($, "ORG_ASSIGNMENT[*].JOBTXT").toString()]`
Target Path 2	$Users.User[*].Organization.Unit[1]
Expression 3	`['Division', jsonPath($, "ORG_ASSIGNMENT[*].ORGTXT").toString()]`
Target Path 3	$Users.User[*].Organization.Unit[2]

Complex Scenarios

Nested Conditional with Multiple Checks:

// Set priority based on multiple conditions
$status == "Critical" ? "P1" :
$status == "High" && $age > 24 ? "P2" :
$status == "Medium" ? "P3" :
"P4"

Combining Date and String Operations:

// Generate timestamped filename
$filename.replace(".csv", "") + "_" +
Date.now().toLocaleDateString({"format":"yyyyMMdd_HHmmss"}) +
".csv"

Data Validation Pattern:

// Validate email format and set to null if invalid
$email.match(/^[^\s@]+@[^\s@]+\.[^\s@]+$/) ? $email : null

Dynamic Field Selection:

// Select field based on environment parameter
_environment == "prod" ? $production_field : $test_field

Safe Navigation with Multiple Levels:

// Safely access nested properties with defaults
$.hasPath("customer.address.city") ?
  $customer.address.city :
  "Unknown"

Array Transformation:

// Transform array of objects to array of specific values
$items.map(item => item.name + " (" + item.id + ")")

Error Rate Calculation:

// Calculate error percentage
{
  "total": snap.in.totalCount,
  "errors": snap.error.totalCount,
  "errorRate": ((snap.error.totalCount / snap.in.totalCount) * 100).toFixed(2) + "%"
}

Best Practices for Expression Examples

Null Safety: Always check for existence before accessing nested properties using hasOwnProperty() or hasPath().
Default Values: Use the OR operator (||) or ternary operator (? :) to provide fallback values.
Readability: Break complex expressions into multiple steps or use intermediate variables when possible.
Performance: Avoid unnecessary function calls in loops or repetitive operations.
Type Consistency: Ensure data types match when performing comparisons or operations.
Date Formatting: Always specify the date format explicitly when parsing or formatting dates.
String Escaping: Properly escape special characters in regular expressions and HTML.
Testing: Test expressions with edge cases including null, empty strings, and missing fields.