JavaScript field

« Page as of 2017-01-23, editions Mobile 4.2.1, Desktop 1.0.7 »

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The value of the field will be the result of execution of the script defined in the field and executed in the entry context.

JavaScript 1.7 is used for scripts. The current version supports only core methods of the language.

A script may consist of multiple operations, but only the result of the last operation will be entered into the field. For example:

var i = 1 + 1  // Result would be 2, if this were the final statement,
i + 1          //   but instead, this is the final statement, so the result will be 3

Fields of an entry

Function field("fieldName") is used to get access to the values of entry fields. The type of the JavaScript object returned by the function depends on the field type.

Compatibility of Memento field types and JavaScript objects is shown in the table:

Field type	JavaScript object
Text , Hyperlink, Password, Phone, Email, Calculation (string result) , Single-choice list , Radio buttons	String
Integer, Real number, Rating, Currency, Calculation (number result)	Number
Date , Date/Time, Time	Date
Checkbox (Boolean)	Boolean
Multiple-choice list, Checkboxes	Array of String
Link to entry	Array of Entry Each array element has a method field() for access to values of fields of entries of the linked library. Example: field("linkField")[i].field("remoteField")

Time of script execution

A script can be executed both when an entry is created or changed and when it is displayed.

The time of script execution is set by the toggle button Execute script real time on the field edit screen. It is reasonable to enable this option if your script contains functions that depend on the current time. Online execution in case of a large number of entries can significantly increase the time required to open the library.

Functions to work with the date

You can enable the integrated library moment.js to work with the date and time. Click JavaScript Libraries and choose moment.min.js.

Some examples. If an entry contains the field Date whose value is 18 March 2016 14:55

Example of date formats

moment(field('Date')).format('MMMMM Do YYYYY')      // March 18th 2016
moment(field('Date')).format('dddd')                // Friday
moment(field('Date')).format('dddd [Escaped] YYYY') // Friday Escaped 2016
moment(field('Date')).format('HH:mm')               // 14:55

Example of relative time

moment(field('Date')).fromNow()                     // 11 minutes ago
moment(field('Date')).startOf('day').fromNow()      // 15 hours ago

Example of calendar time

moment(field('Date')).calendar()                    // Today at 2:55 PM
moment(field('Date')).add(1 , 'days').calendar()    // Tomorrow at 2:55 PM

More information about library features on [1]

Examples

Example: Sum

Entries contain fields: Price, Count. We add a JavaScript field "Sum" by using the following script:

field('Price')*field('Count')

Example: Percentage

Entries contain fields: Count, Total. We add a JavaScript field "Percentage" by using the following script:

var total = field('Total')
if (total > 0)
   field('Count')*100/total + ' %'
else
   'none'

Example: Days

Entries contain fields: StartDateTime, EndDateTime. We add a calculating field "Days" by using the following script:

moment(field('End')).diff(field('Start') , 'days')

Example: References

There’s library Order – with orders and library Item – with items. Library Order contains a link to library Item. Library Item contains field Price. To calculate the cost of the order, let’s add script field Sum using the following script:

var sum = 0
var items = field('Item')
for(var i in items) {
   sum = sum + items[i].field('Price')
}

Example: Birthday

We have a birthday field. If a person is younger than 18 years old, we want to display the string "youth", otherwise the string "adult".

var years = moment().diff(field('Birthday') , 'years' )
if (years < 18)
   'Youth'
else
   'Adult'

Examples of calculations on linked entries

If you have a many-to-many Link To Entry field — linking the current entry to zero or more entries in another library — and if you have an amount field in that other library, you may want to perform calculations on that field across those entries, in similar fashion to Memento aggregation functions.

Example: Sum of linked amounts

var amountField = "Amount";        // CHANGE Amount to your amount field name
var linkedEntries = field("Them"); // CHANGE Them to your link field name
var numLE = linkedEntries.length;  // The number of linked entries

// Loop through linked entries, creating the sum
for (var lex = 0, result = 0; lex < numLE; lex++)
    result += linkedEntries[lex].field(amountField);

result;                            // The result is the SUM

Example: Average of linked amounts

var amountField = "Amount";        // CHANGE Amount to your amount field name
var linkedEntries = field("Them"); // CHANGE Them to your link field name
var numLE = linkedEntries.length;  // The number of linked entries

// Loop through linked entries, creating the sum
for (var lex = 0, result = 0; lex < numLE; lex++)
    result += linkedEntries[lex].field(amountField);

if (numLE != 0)
    result / numLE;                // The result is the AVERAGE

Example: Minimum of linked amounts

var amountField = "Amount";        // CHANGE Amount to your amount field name
var linkedEntries = field("Them"); // CHANGE Them to your link field name
var numLE = linkedEntries.length;  // The number of linked entries
var temp;

// Loop through linked entries, finding the MINIMUM
for (var lex = 0, result = 0; lex < numLE; lex++) {
    temp = linkedEntries[lex].field(amountField);
    if (temp < result)
        result = temp;
    }

result;                            // The result is the MINIMUM

Example: Maximum of linked amounts

var amountField = "Amount";        // CHANGE Amount to your amount field name
var linkedEntries = field("Them"); // CHANGE Them to your link field name
var numLE = linkedEntries.length;  // The number of linked entries
var temp;

// Loop through linked entries, finding the MAXIMUM
for (var lex = 0, result = 0; lex < numLE; lex++) {
    temp = linkedEntries[lex].field(amountField);
    if (temp > result)
        result = temp;
    }

result;                            // The result is the MAXIMUM

References

You can find a full description of the language here. The implementation is based on the Rhino library.

Name

Textual, case-insensitive field identifier that can include spaces; it's best to avoid characters that can be used as operators, though (standard across all field types)

Hint

Textual, case-insensitive field identifier that can include spaces

Script

Script itself

JavaScript script. The context of the script is the Entry object. The value returned is the last value assigned or expressed.

JavaScript Libraries

Choose additional JavaScript Libraries to be loaded. At this time, only moment.min.js is available.

Execute script in real time

No (default)

Script will run only upon edit. Performance will be enhanced.

Yes

Script will run upon edit or display.

Display Options

Display in the list as

Select among the following roles for the current field:

• As a Regular field
• As an Entry Name
• As an Entry Description
• As an Entry Status

The field name

Display the name of the field in the card entry (By default, On). By this, it is meant that the field name will or will not be displayed on either the Entry View card or the Entry Edit card.

Font

Choices are:

• Family: Regular, Light, Condensed, Thin, Medium. By default, Regular.
• Style: Normal, Bold, Italic, Bold Italic. By default, Normal.
• Size: By default, 18. Direct entry to change.
• Color: By default, White. Palette of 20 colors, backed up by a continuously variable color chooser.

Dependencies

Ability to add one or more visibility dependencies upon fields with qualifying types.

JavaScript links

W3Schools
JavaScript Tutorial	A pleasant, fairly complete, and useful tutorial on JavaScript Best on a computer or tablet in landscape. On a phone or tablet in portrait, scroll to the bottom for navigation.
Mozilla Developer Network
JavaScript Guide	Shows you how to use JavaScript, gives an overview of the language, and presents its capabilities & features
JavaScript Reference	The entire JavaScript language described in detail
Introduction to JavaScript	Introduces JavaScript and discusses some of its fundamental concepts
JavaScript Tutorial	A re-introduction. JavaScript is often derided as being a toy, but beneath its simplicity, powerful language features await.
JavaScript 1.7	The JavaScript release upon which Memento is currently based
About JavaScript	Jumping off point in learning about JavaScript

[Category:Spec]