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utils.js (2344B)

      1 /**
      2  * This file contains a list of utility functions which are useful in other
      3  * files.
      4  */
      5 
      6 /**
      7  * Provide an `indexOf` function which works in IE8, but defers to native if
      8  * possible.
      9  */
     10 const nativeIndexOf = Array.prototype.indexOf;
     11 const indexOf = function(list, elem) {
     12     if (list == null) {
     13         return -1;
     14     }
     15     if (nativeIndexOf && list.indexOf === nativeIndexOf) {
     16         return list.indexOf(elem);
     17     }
     18     const l = list.length;
     19     for (let i = 0; i < l; i++) {
     20         if (list[i] === elem) {
     21             return i;
     22         }
     23     }
     24     return -1;
     25 };
     26 
     27 /**
     28  * Return whether an element is contained in a list
     29  */
     30 const contains = function(list, elem) {
     31     return indexOf(list, elem) !== -1;
     32 };
     33 
     34 /**
     35  * Provide a default value if a setting is undefined
     36  */
     37 const deflt = function(setting, defaultIfUndefined) {
     38     return setting === undefined ? defaultIfUndefined : setting;
     39 };
     40 
     41 // hyphenate and escape adapted from Facebook's React under Apache 2 license
     42 
     43 const uppercase = /([A-Z])/g;
     44 const hyphenate = function(str) {
     45     return str.replace(uppercase, "-$1").toLowerCase();
     46 };
     47 
     48 const ESCAPE_LOOKUP = {
     49     "&": "&amp;",
     50     ">": "&gt;",
     51     "<": "&lt;",
     52     "\"": "&quot;",
     53     "'": "&#x27;",
     54 };
     55 
     56 const ESCAPE_REGEX = /[&><"']/g;
     57 
     58 function escaper(match) {
     59     return ESCAPE_LOOKUP[match];
     60 }
     61 
     62 /**
     63  * Escapes text to prevent scripting attacks.
     64  *
     65  * @param {*} text Text value to escape.
     66  * @return {string} An escaped string.
     67  */
     68 function escape(text) {
     69     return ("" + text).replace(ESCAPE_REGEX, escaper);
     70 }
     71 
     72 /**
     73  * A function to set the text content of a DOM element in all supported
     74  * browsers. Note that we don't define this if there is no document.
     75  */
     76 let setTextContent;
     77 if (typeof document !== "undefined") {
     78     const testNode = document.createElement("span");
     79     if ("textContent" in testNode) {
     80         setTextContent = function(node, text) {
     81             node.textContent = text;
     82         };
     83     } else {
     84         setTextContent = function(node, text) {
     85             node.innerText = text;
     86         };
     87     }
     88 }
     89 
     90 /**
     91  * A function to clear a node.
     92  */
     93 function clearNode(node) {
     94     setTextContent(node, "");
     95 }
     96 
     97 module.exports = {
     98     contains: contains,
     99     deflt: deflt,
    100     escape: escape,
    101     hyphenate: hyphenate,
    102     indexOf: indexOf,
    103     setTextContent: setTextContent,
    104     clearNode: clearNode,
    105 };