refactor: replace remaining substr in test files

Fixed remaining deprecated substr() calls in build/test files:
- test/strict-d3.js
- test/jasmine/assets/domain_ref_components.js
- test/jasmine/bundle_tests/no_webgl_test.js
- test/jasmine/assets/custom_assertions.js
- test/jasmine/bundle_tests/plotschema_test.js

Excluded stackgl_modules as requested.

Author: JBR-0100

test/jasmine/assets/custom_assertions.js

@@ -226,7 +226,7 @@ exports.assertClip = function(sel, isClipped, size, msg) {
         var clipPath = d3Select(this).attr('clip-path');
 
         if(isClipped) {
-            expect(String(clipPath).substr(0, 4))
+            expect(String(clipPath).slice(0, 4))
                 .toBe('url(', msg + ' clip path ' + '(item ' + i + ')');
         } else {
             expect(clipPath)

test/jasmine/assets/domain_ref_components.js

@@ -586,8 +586,8 @@ function testShapeCombo(combo, assert, gd) {
     var xaroPos = combo[3];
     var yaroPos = combo[4];
     var shapeType = combo[5];
-    var xAxNum = axispair[0].substr(1);
-    var yAxNum = axispair[1].substr(1);
+    var xAxNum = axispair[0].slice(1);
+    var yAxNum = axispair[1].slice(1);
     return Plotly.newPlot(gd, Lib.extendDeep({}, testMock))
         .then(function(gd) {
             return shapeTest(gd,

test/jasmine/bundle_tests/no_webgl_test.js

@@ -19,7 +19,7 @@ describe('Plotly w/o WebGL support:', function() {
     function checkNoWebGLMsg(visible) {
         var msg = gd.querySelector('div.no-webgl > p');
         if(visible) {
-            expect(msg.innerHTML.substr(0, 22)).toBe('WebGL is not supported');
+            expect(msg.innerHTML.slice(0, 22)).toBe('WebGL is not supported');
         } else {
             expect(msg).toBe(null);
         }

test/jasmine/bundle_tests/plotschema_test.js

@@ -172,7 +172,7 @@ describe('plot schema', function() {
             );
 
             var name = np.parts[np.parts.length - 1];
-            var itemName = name.substr(0, name.length - 1);
+            var itemName = name.slice(0, name.length - 1);
 
             var itemsObj = np.get().items;
             var itemObj = itemsObj[itemName];

test/strict-d3.js

@@ -71,7 +71,7 @@ function checkStyleVal(sel, key, val) {
         // test each part separately
         val.split(/[, ]/g).forEach(function(valPart) {
             var pxSplit = valPart.length - 2;
-            if(valPart.substr(pxSplit) === 'px' && !isNumeric(valPart.substr(0, pxSplit))) {
+            if(valPart.slice(pxSplit) === 'px' && !isNumeric(valPart.slice(0, pxSplit))) {
                 throw new Error('d3 selection.style called with value: ' + val);
             }
         });