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JS.Evaluate

Evaluates a JavaScript expression.

Component Version macOS Windows Linux Server iOS SDK
JavaScript 10.0 ✅ Yes ✅ Yes ✅ Yes ✅ Yes ✅ Yes
MBS( "JS.Evaluate"; JSRef; JavaScript )   More

Parameters

Parameter Description Example
JSRef The JavaScript reference number. $js
JavaScript A JavaScript expression. "1+2"

Result

Returns JSON or error.

Description

Evaluates a JavaScript expression.
This may include definition of functions and objects and using them.
Result is converted to JSON and returned.

The evaluate runs within the FileMaker process. If you cause an endless loop, FileMaker freezes and needs to be force quit, so please always include an exit condition for your loops. Also if you get JavaScript to crash, FileMaker will crash with it.

Examples

Evaluate some expressions:

Set Variable [ $js ; Value: MBS( "JS.New" ) ]
Set Variable [ $r ; Value: MBS( "JS.Evaluate"; $js; "4+5") ]
Show Custom Dialog [ "Result" ; $r ]
Set Variable [ $r ; Value: MBS( "JS.SetGlobalProperty"; $JS; "test"; "\"Hello World\"" ) ]
Set Variable [ $r ; Value: MBS( "JS.Evaluate"; $js; "test + test;") ]
Show Custom Dialog [ "Result" ; $r ]
Set Variable [ $r ; Value: MBS( "JS.Release"; $JS ) ]

Defines and runs a function in JavaScript:

Let([
f = "
function makeCRCTable(){
        var c;
        var crcTable = [];
        for(var n =0; n < 256; n++){
                c = n;
                for(var k =0; k < 8; k++){
                        c = ((c&1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1));
                }
                crcTable[n] = c;
        }
        return crcTable;
}

function crc32(str) {
        var crcTable = crcTable || (crcTable = makeCRCTable());
        var crc = 0 ^ (-1);

        for (var i = 0; i < str.length; i++ ) {
                crc = (crc >>> 8) ^ crcTable[(crc ^ str.charCodeAt(i)) & 0xFF];
        }

        return (crc ^ (-1)) >>> 0;
};

crc32(InputValue);";
j = MBS( "JS.New" );
r = MBS( "JS.SetGlobalPropertyValue"; j; "InputValue"; "Hello World" );
r = MBS( "JS.Evaluate"; j; f );
x = MBS( "JS.Release"; j )
];r)

Initialize JavaScript environment with two functions:

If [ Length($$js) = 0 ]
    Set Variable [ $$js ; Value: MBS( "JS.New" ) ]
    Set Variable [ $r ; Value: MBS( "JS.Evaluate"; $$js;
"function makeCRCTable(){
                var c;
                var crcTable = [];
                for(var n =0; n < 256; n++){
                                c = n;
                                for(var k =0; k < 8; k++){
                                                c = ((c&1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1));
                                }
                                crcTable[n] = c;
                }
                return crcTable;
}

function crc32(str) {
                var crcTable = crcTable || (crcTable = makeCRCTable());
                var crc = 0 ^ (-1);

                for (var i = 0; i < str.length; i++ ) {
                                crc = (crc >>> 8) ^ crcTable[(crc ^ str.charCodeAt(i)) & 0xFF];
                }

                return (crc ^ (-1)) >>> 0;
};") ]
End If

List global properties:

MBS( "JS.Evaluate"; $$JS; "Object.keys(globalThis);" )

Query now in JavaScript:

MBS( "JS.Evaluate"; $$JS; "performance.now();" )

Measure tikem for a test function:

MBS("JS.Evaluate"; $js; "function testFunction() {
        for (var i = 0; i < 1e6; i++) {}
}

var t1 = performance.now();
testFunction();
var t2 = performance.now();

('test took: ' + (t2 - t1) + ' milliseconds');")

See also

Example Databases

Blog Entries

This function checks for a license.

Created 7th December 2019, last changed 8th July 2024


JS.CallFunctionValues - JS.EvaluateToString