throttle selectArea on mousemove

lib/frappe-datatable.js

@@ -277,6 +277,7 @@ exports.buildCSSRule = buildCSSRule;
 exports.removeCSSRule = removeCSSRule;
 exports.copyTextToClipboard = copyTextToClipboard;
 exports.isNumeric = isNumeric;
+exports.throttle = throttle;
 function camelCaseToDash(str) {
   return str.replace(/([A-Z])/g, function (g) {
     return '-' + g[0].toLowerCase();
@@ -433,6 +434,41 @@ function isNumeric(val) {
   return !isNaN(val);
 }
 
+// https://stackoverflow.com/a/27078401
+function throttle(func, wait, options) {
+  var context, args, result;
+  var timeout = null;
+  var previous = 0;
+  if (!options) options = {};
+
+  var later = function later() {
+    previous = options.leading === false ? 0 : Date.now();
+    timeout = null;
+    result = func.apply(context, args);
+    if (!timeout) context = args = null;
+  };
+
+  return function () {
+    var now = Date.now();
+    if (!previous && options.leading === false) previous = now;
+    var remaining = wait - (now - previous);
+    context = this;
+    args = arguments;
+    if (remaining <= 0 || remaining > wait) {
+      if (timeout) {
+        clearTimeout(timeout);
+        timeout = null;
+      }
+      previous = now;
+      result = func.apply(context, args);
+      if (!timeout) context = args = null;
+    } else if (!timeout && options.trailing !== false) {
+      timeout = setTimeout(later, remaining);
+    }
+    return result;
+  };
+};
+
 /***/ }),
 /* 2 */
 /***/ (function(module, exports, __webpack_require__) {
@@ -663,10 +699,12 @@ var CellManager = function () {
         mouseDown = false;
       });
 
-      _dom2.default.on(this.bodyScrollable, 'mousemove', '.data-table-col', function (e) {
+      var selectArea = function selectArea(e) {
         if (!mouseDown) return;
         _this5.selectArea((0, _dom2.default)(e.delegatedTarget));
-      });
+      };
+
+      _dom2.default.on(this.bodyScrollable, 'mousemove', '.data-table-col', (0, _utils.throttle)(selectArea, 100));
     }
   }, {
     key: 'focusCell',

src/cellmanager.js

@@ -1,6 +1,7 @@
 import {
   copyTextToClipboard,
-  makeDataAttributeString
+  makeDataAttributeString,
+  throttle
 } from './utils';
 import keyboard from './keyboard';
 import $ from './dom';
@@ -169,10 +170,12 @@ export default class CellManager {
       mouseDown = false;
     });
 
-    $.on(this.bodyScrollable, 'mousemove', '.data-table-col', (e) => {
+    const selectArea = (e) => {
       if (!mouseDown) return;
       this.selectArea($(e.delegatedTarget));
-    });
+    };
+
+    $.on(this.bodyScrollable, 'mousemove', '.data-table-col', throttle(selectArea, 100));
   }
 
   focusCell($cell, { skipClearSelection = 0 } = {}) {

src/utils.js

@@ -147,3 +147,38 @@ export function copyTextToClipboard(text) {
 export function isNumeric(val) {
   return !isNaN(val);
 }
+
+// https://stackoverflow.com/a/27078401
+export function throttle(func, wait, options) {
+  var context, args, result;
+  var timeout = null;
+  var previous = 0;
+  if (!options) options = {};
+
+  let later = function () {
+    previous = options.leading === false ? 0 : Date.now();
+    timeout = null;
+    result = func.apply(context, args);
+    if (!timeout) context = args = null;
+  };
+
+  return function () {
+    var now = Date.now();
+    if (!previous && options.leading === false) previous = now;
+    let remaining = wait - (now - previous);
+    context = this;
+    args = arguments;
+    if (remaining <= 0 || remaining > wait) {
+      if (timeout) {
+        clearTimeout(timeout);
+        timeout = null;
+      }
+      previous = now;
+      result = func.apply(context, args);
+      if (!timeout) context = args = null;
+    } else if (!timeout && options.trailing !== false) {
+      timeout = setTimeout(later, remaining);
+    }
+    return result;
+  };
+};