| 1 | // Minimal AJAX library.
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| 2 | //
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| 3 | // The motivation is that we want to generate PNG, JSON, CSV, etc. from R.
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| 4 | // And maybe some HTML fragments. But we don't want to generate a different
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| 5 | // skeleton for every page. It's nice just to hit F5 and see the changes
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| 6 | // reloaded. It's like "PHP in the browser'.
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| 7 |
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| 8 | 'use strict';
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| 9 |
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| 10 | // Append a message to an element. Used for errors.
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| 11 | function appendMessage(elem, msg) {
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| 12 | elem.innerHTML += msg + '<br />';
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| 13 | }
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| 14 |
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| 15 | // jQuery-like AJAX helper, but simpler.
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| 16 |
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| 17 | // Requires an element with id "status" to show errors.
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| 18 | //
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| 19 | // Args:
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| 20 | // errElem: optional element to append error messages to. If null, then
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| 21 | // alert() on error.
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| 22 | // success: callback that is passed the xhr object.
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| 23 | function ajaxGet(url, errElem, success) {
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| 24 | var xhr = new XMLHttpRequest();
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| 25 | xhr.open('GET', url, true /*async*/);
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| 26 | xhr.onreadystatechange = function() {
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| 27 | if (xhr.readyState != 4 /*DONE*/) {
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| 28 | return;
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| 29 | }
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| 30 |
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| 31 | if (xhr.status != 200) {
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| 32 | var msg = 'ERROR requesting ' + url + ': ' + xhr.status + ' ' +
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| 33 | xhr.statusText;
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| 34 | if (errElem) {
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| 35 | appendMessage(errElem, msg);
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| 36 | } else {
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| 37 | alert(msg);
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| 38 | }
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| 39 | return;
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| 40 | }
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| 41 |
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| 42 | success(xhr);
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| 43 | };
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| 44 | xhr.send();
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| 45 | }
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| 46 |
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| 47 | function jsonGet(url, errElem, success) {
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| 48 | ajaxGet(url, errElem, function(xhr) {
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| 49 | try {
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| 50 | var j = JSON.parse(xhr.responseText);
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| 51 | } catch (e) {
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| 52 | appendMessage(errElem, `Parsing JSON in ${url} failed`);
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| 53 | }
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| 54 | success(j);
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| 55 | });
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| 56 | }
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| 57 |
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| 58 | function htmlEscape(unsafe) {
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| 59 | return unsafe
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| 60 | .replace(/&/g, "&")
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| 61 | .replace(/</g, "<")
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| 62 | .replace(/>/g, ">")
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| 63 | .replace(/"/g, """)
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| 64 | .replace(/'/g, "'");
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| 65 | }
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| 66 |
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| 67 | //
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| 68 | // UrlHash
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| 69 | //
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| 70 |
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| 71 | // helper
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| 72 | function _decode(s) {
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| 73 | var obj = {};
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| 74 | var parts = s.split('&');
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| 75 | for (var i = 0; i < parts.length; ++i) {
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| 76 | if (parts[i].length === 0) {
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| 77 | continue; // quirk: ''.split('&') is [''] ? Should be a 0-length array.
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| 78 | }
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| 79 | var pair = parts[i].split('=');
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| 80 | obj[pair[0]] = pair[1]; // for now, assuming no =
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| 81 | }
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| 82 | return obj;
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| 83 | }
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| 84 |
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| 85 | function _encode(d) {
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| 86 | var parts = [];
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| 87 | for (var name in d) {
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| 88 | var s = name;
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| 89 | s += '=';
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| 90 | var value = d[name];
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| 91 | s += encodeURIComponent(value);
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| 92 | parts.push(s);
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| 93 | }
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| 94 | return parts.join('&');
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| 95 | }
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| 96 |
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| 97 |
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| 98 | // UrlHash Constructor.
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| 99 | // Args:
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| 100 | // hashStr: location.hash
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| 101 | function UrlHash(hashStr) {
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| 102 | this.reset(hashStr);
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| 103 | }
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| 104 |
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| 105 | UrlHash.prototype.reset = function(hashStr) {
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| 106 | var h = hashStr.substring(1); // without leading #
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| 107 | // Internal storage is string -> string
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| 108 | this.dict = _decode(h);
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| 109 | }
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| 110 |
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| 111 | UrlHash.prototype.set = function(name, value) {
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| 112 | this.dict[name] = value;
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| 113 | };
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| 114 |
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| 115 | UrlHash.prototype.del = function(name) {
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| 116 | delete this.dict[name];
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| 117 | };
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| 118 |
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| 119 | UrlHash.prototype.get = function(name ) {
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| 120 | return this.dict[name];
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| 121 | };
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| 122 |
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| 123 | // e.g. Table states have keys which start with 't:'.
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| 124 | UrlHash.prototype.getKeysWithPrefix = function(prefix) {
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| 125 | var keys = [];
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| 126 | for (var name in this.dict) {
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| 127 | if (name.indexOf(prefix) === 0) {
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| 128 | keys.push(name);
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| 129 | }
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| 130 | }
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| 131 | return keys;
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| 132 | };
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| 133 |
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| 134 | // Return a string reflecting internal key-value pairs.
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| 135 | UrlHash.prototype.encode = function() {
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| 136 | return _encode(this.dict);
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| 137 | };
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| 138 |
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| 139 | // Useful for AJAX navigation. If UrlHash is the state of the current page,
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| 140 | // then we override the state with 'attrs' and then return a serialized query
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| 141 | // fragment.
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| 142 | UrlHash.prototype.modifyAndEncode = function(attrs) {
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| 143 | var copy = {}
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| 144 | // NOTE: Object.assign is ES6-only
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| 145 | // https://googlechrome.github.io/samples/object-assign-es6/
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| 146 | Object.assign(copy, this.dict, attrs);
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| 147 | return _encode(copy);
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| 148 | };
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| 149 |
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