Originally from earlduque/ServiceNow-Developer-Training. Thanks Earl!

Client Scripts in ServiceNow #

Table of Contents #


Types of Scripts

Script Types

GlideForm API


Other Things to Try

Overview #

What are Client Scripts?

  • Client scripts are used to customize features using JavaScript
  • You can use scripts to run on server as well as client browsers
  • Since servers have direct access to the database server scripts are used to modify records in the DB and generate events
  • Since the client has access to forms, client scripts are used to tailor forms to the current user and conditions
  • Client Scripts can be used to configure forms, form fields, and form values in real time while user is using the form

Some of the things that client scripts can do include:

  • Place the cursor in a form field on form load
  • Generate alerts, confirmations, and messages
  • Populate a form field in response to another field's value
  • Highlight a form field
  • Validate form data
  • Modify choice list options
  • Hide/Show fields or sections
  • Modify options in choice list depending on a users role
  • Display messages based on the value in another field

Note: to view all Client Scripts in your ServiceNow instance, head to System Definition > Client Scripts or type "Client Scripts" in the navigator

Script Types #

There are a few different kinds of scripts:

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  • an onLoad() script which controls how the form first appears to the user; in other words, how the page loads.

  • an onChange() scripts which changes the form when the user changes a field, which is useful for automatically setting the value of a field, or displaying a message depending on the value(s) a user enters
    screen shot 2019-01-25 at 1 24 22 pm

  • an onSubmit() script which runs when the user submits the form, which is useful for validating values that the user entered.
    screen shot 2019-01-25 at 1 24 28 pm

  • an onCellEdit() is similar to an onChange() function, except the script runs when a user changes a field on a list rather than a form. (But we don't really need to worry about this one)

GlideForm API #

Client scripts configure forms and their fields/values through an API (Application Programming Interface) called GlideForm. You can call GlideForm API through g_form to do things like: highlight area, get info or set value for field
change choices in a list


function onLoad() {
g_form.removeOption("priority", "1");

Here's a list of g_form methods you can use which allow you to do the following:

  • Draw attention: flash(), showFieldMsg()
  • Get information: getValue(), getReference()
  • Change a field value: setValue(), clearValue()
  • Change a choice list: addOptions(), clearOptions()
  • Get field information: getSections(), isNewRecord()
  • Form actions: addInfoMessage(), clearMessages()

g_user Glide User methods provide information about the current user through the global g_user object

g_user Methods Properties
getClientData() firstName
getFullName() lastName
hasRole() userID
hasRoleExactly() userName


function onLoad() {
if (g_user.hasRole("itil_admin")) {

g_record Glide Record methods make calls to the database on the server without having to use mySQL and uses the gr object.


function onSubmit() {
var gr = new GlideRecord(g_form.getTableName);
if (!gr.get(g_form.getUniqueValue())) {

The GlideAjax API sends work to the server using a script include with the ajax object.


function onChange() {
if (newValue === "") {
var ajax = new GlideAjax("AssessmentUtilsAjax");
ajax.addParam("sysparm_metricJ_type", String(newValue));
ajax.addParam("sysparm_name", "GetMetricTypeTable");
ajax.getXML(function(response) {
if (response) {
var table = response.responseXML.documentElement.getAttribute(
g_form.setValue("table", "table");

Tutorial #

Here is a tutorial on making your first client script using JavaScript and the GlideForm API. We are just going to do some simple date validation.

1. Make sure you use your personal developer instance of ServiceNow before continuing onto the next step.

2. In your navigation bar, search for "Maintain Items" and head to that page.

3. Create a new Catalog Item called "About Me" (you can name it something else if you'd like)

4. Fill out the short description and hit 'Submit'

5. Create two new variables to start: Full Name (type: Single Line Text) and Birthdate (type: Date)

6. After creating your new variables, scroll down to the bottom of the page and select Catalog Client Scripts

7. Select New
screen shot 2019-01-30 at 12 22 16 pm
8. Make sure to select "Mobile/Service Portal"
screen shot 2019-01-30 at 12 06 44 pm

9. We're going to create an onChange() client script to verify that the user filling out the form selects a date in the past. So on the upper right side of the form, select onChange() under the Type field.

10. Select the birthdate variable you created earlier

screen shot 2019-01-30 at 12 06 14 pm

11. Make sure that the checkbox for Applies to a Catalog Item View is checked.

12. After onChange() has been selected, the Script field should automatically be filled with a generic onChange() function. If not, copy and paste the following code:

function onChange(control, oldValue, newValue, isLoading) {
if (isLoading || newValue == "") {

//Type appropriate comment here, and begin script below

13. Since we need to access a form value, we are going to use the g_form API we mentioned earlier. Underneath the closing bracket of the if statement, create a new variable (here we are calling it dat) and assign it to a g_form.getValue() method which selects the birthdate variable in order to access the value selected by the user, like this:

var dat = g_form.getValue("birthdate");

14. Since we need to compare Date() objects, we next need to declare a new variable called bday and assign it to a new Date() object which takes dat as an argument.

15. Next, we need to make sure that the date selected is not a future date, since you obviously were not born in the future. So now we create a new variable called today and assign it to a a new Date() object as well. If given no arguments, the JavaScript Date() object defaults to the current date: var today = new Date();

16. Next, we need an if statement which takes a condition that compares the two Date() objects. This is done to check if the bday value is less than today in order to see if the birthdate is a future date, which is not an acceptable value.

17. Inside the if statement, we want to a window pop up to alert the user that the date they've selected an invalid date if the if statement condition evaluates to true. The alert() window should read something like this: "The date selected is in the future, please select a date in the past"

18. Next, we want to reset the Birthdate field since we need the user to reselect a new date. Again, we are going to use the g_form API to set the birthdate value to empty by using gform's setValue() method. setValue takes two arguments, the first being the _variable of which you wish to set, the second argument being the value you wish to set the variable to. By now your code should resemble this:

function onChange(control, oldValue, newValue, isLoading) {
if (isLoading || newValue == "") {
var dat = g_form.getValue("birthdate");
var bday = new Date(dat);
var today = new Date();
if (bday > today) {
"The date selected is in the future, please select a date in the past"
g_form.setValue("birthdate", "");

19. Now, click Update & Exit. This should redirect you to your Catalog Item.

20. On the upper right corner of the page, click Try It

21. Fill out the About Me form and try to choose a future date as your birthday.

22. You should see an alert window tell you that your choice is invalid. When you close the alert message, you should see that the Birthdate field has been set to empty.

Congratulations! You've just created your first client script. #

Other things to try: #

  • Adding a few more fields and creating an onLoad() that autofills the user and email fields.
  • Instead of having a date validation onChange() script, make it so that the date is validated until the form is submitted using an onSubmit script.
  • Use onSubmit() to produce a pop up window asking if the user is sure that they want to submit the form. Only submit if the user selects "Yes".
  • Depending on a previously selected value, modify the options on a list of a following field.
  • Produce an error message using onChange() (instead of a pop up) alerting the user that their selection/input is invalid.