jquery/jquery

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src/css/adjustCSS.js

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Maintainability
A
1 hr
Test Coverage
define( [
    "../core",
    "./isAutoPx",
    "../var/rcssNum"
], function( jQuery, isAutoPx, rcssNum ) {

"use strict";

function adjustCSS( elem, prop, valueParts, tween ) {
    var adjusted, scale,
        maxIterations = 20,
        currentValue = tween ?
            function() {
                return tween.cur();
            } :
            function() {
                return jQuery.css( elem, prop, "" );
            },
        initial = currentValue(),
        unit = valueParts && valueParts[ 3 ] || ( isAutoPx( prop ) ? "px" : "" ),

        // Starting value computation is required for potential unit mismatches
        initialInUnit = elem.nodeType &&
            ( !isAutoPx( prop ) || unit !== "px" && +initial ) &&
            rcssNum.exec( jQuery.css( elem, prop ) );

    if ( initialInUnit && initialInUnit[ 3 ] !== unit ) {

        // Support: Firefox <=54 - 66+
        // Halve the iteration target value to prevent interference from CSS upper bounds (gh-2144)
        initial = initial / 2;

        // Trust units reported by jQuery.css
        unit = unit || initialInUnit[ 3 ];

        // Iteratively approximate from a nonzero starting point
        initialInUnit = +initial || 1;

        while ( maxIterations-- ) {

            // Evaluate and update our best guess (doubling guesses that zero out).
            // Finish if the scale equals or crosses 1 (making the old*new product non-positive).
            jQuery.style( elem, prop, initialInUnit + unit );
            if ( ( 1 - scale ) * ( 1 - ( scale = currentValue() / initial || 0.5 ) ) <= 0 ) {
                maxIterations = 0;
            }
            initialInUnit = initialInUnit / scale;

        }

        initialInUnit = initialInUnit * 2;
        jQuery.style( elem, prop, initialInUnit + unit );

        // Make sure we update the tween properties later on
        valueParts = valueParts || [];
    }

    if ( valueParts ) {
        initialInUnit = +initialInUnit || +initial || 0;

        // Apply relative offset (+=/-=) if specified
        adjusted = valueParts[ 1 ] ?
            initialInUnit + ( valueParts[ 1 ] + 1 ) * valueParts[ 2 ] :
            +valueParts[ 2 ];
        if ( tween ) {
            tween.unit = unit;
            tween.start = initialInUnit;
            tween.end = adjusted;
        }
    }
    return adjusted;
}

return adjustCSS;
} );