require the number to be finite, and not in scientific notation if it…

…'s non-integer, #109
phetsims · Aug 17, 2021 · 90df01f · 90df01f
1 parent 6a11351
commit 90df01f
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Showing 2 changed files with 17 additions and 1 deletion.
diff --git a/js/Utils.js b/js/Utils.js
@@ -823,14 +823,16 @@ const Utils = {
 
   /**
    * Determines the number of decimal places in a value.
-   * @param {number} value
+   * @param {number} value - a finite number, scientific notation is not supported for decimal numbers
    * @returns {number}
    */
   numberOfDecimalPlaces( value ) {
+    assert && assert( typeof value === 'number' && isFinite( value ), `value must be a finite number ${value}` );
     if ( Math.floor( value ) === value ) {
       return 0;
     }
     else {
+      assert && assert( !value.toString().includes( 'e' ), `scientific notation is not supported: ${value}` );
       return value.toString().split( '.' )[ 1 ].length;
     }
   },

diff --git a/js/UtilsTests.js b/js/UtilsTests.js
@@ -161,6 +161,8 @@ QUnit.test( 'toDegrees', assert => {
 } );
 
 QUnit.test( 'numberOfDecimalPlaces', assert => {
+
+  // Tests that should succeed.
   assert.equal( Utils.numberOfDecimalPlaces( 10 ), 0 );
   assert.equal( Utils.numberOfDecimalPlaces( -10 ), 0 );
   assert.equal( Utils.numberOfDecimalPlaces( 10.1 ), 1 );
@@ -172,6 +174,18 @@ QUnit.test( 'numberOfDecimalPlaces', assert => {
   assert.equal( Utils.numberOfDecimalPlaces( 0.001 ), 3 );
   assert.equal( Utils.numberOfDecimalPlaces( -0.001 ), 3 );
   assert.equal( Utils.numberOfDecimalPlaces( 0.56 ), 2 );
+  assert.equal( Utils.numberOfDecimalPlaces( 1e50 ), 0 ); // scientific notation is supported for integers
+
+  // Tests that should fail.
+  window.assert && assert.throws( () => {
+    Utils.numberOfDecimalPlaces( 'foo' );
+  }, 'value must be a number' );
+  window.assert && assert.throws( () => {
+    Utils.numberOfDecimalPlaces( Infinity );
+  }, 'value must be a finite number' );
+  window.assert && assert.throws( () => {
+    Utils.numberOfDecimalPlaces( 1e-50 );
+  }, 'scientific notation is not supported for decimals' );
 } );
 
 QUnit.test( 'roundToInterval', assert => {