修改random

CreatorUtils/RandomUtils.js

@@ -0,0 +1,82 @@
+/**------------es6 环境------------ */
+/** 参考http://taobaofed.org/blog/2015/12/07/some-thing-about-random/ **/
+
+/**
+ * 案例
+ * let obj = ['登山包', '旅行箱', '移动电源', '不中奖'];
+   ratio=[0.01,0.03,0.06,0.9]
+ */
+function updateRandom() {
+    let p = Math.random(), n = Math.random() / 4;
+    if (p < 0.01) {
+        return 0 + n;
+    }
+    if (p < 0.04) {
+        return 0.25 + n;
+    }
+    if (p < 0.1) {
+        return 0.5 + n;
+    }
+    if (p < 1) {
+        return 0.75 + n;
+    }
+}
+
+/**
+ * 
+ * @param {*} weights 
+ */
+function randomInProbability(weights) {
+    if (arguments.length > 1) {
+        weights = [].slice.call(arguments);
+    }
+
+    let total, current = 0, parts = [], i = 0, l = weights.length;
+    total = weights.reduce ? weights.reduce((a, b) => a + b) : eval(weights.join('+'));
+
+    for (; i < l; i++) {
+        current += weights[i];
+        parts.push('if(p<', current / total, ') return ', i / l, ' + n;');
+    }
+
+    return Function('var p=Math.random(),n=Math.random()/' + l + ';' + parts.join(''));
+}
+
+
+function testRandom(times, random, obj) {
+    let result = new Array(obj.length);
+    result.fill(0);
+    let statisticTimes = times;
+    for (let i = 0; i < statisticTimes; i++) {
+        randomIdx = Math.floor(obj.length * random());
+        result[randomIdx]++;
+    }
+
+    let statistics = result.map((value) => {
+        return value / statisticTimes;
+    });
+    let count = result.reduce((accumulateor, currentValue) => accumulateor + currentValue);
+
+    console.log('count', count, 'statistics=', statistics);
+}
+
+/**-------------------------------------------------------- */
+
+var model = [];
+
+for (var i = 0; i < 100; i++) {
+    model.push(2 + Math.sin(Math.PI * 2 * i / 50));
+}
+console.log('model', model);
+
+let obj = ['登山包', '旅行箱', '移动电源', '不中奖'];
+
+testRandom(100000, updateRandom, obj);
+
+testRandom(100000, randomInProbability(0.01, 0.03, 0.06, 0.9), obj);
+
+testRandom(100000, randomInProbability(model), model);
+
+
+
+