upload

src/er.js

+var _ = require("lodash");
+
+var getEr = function(iDielectricConst, iImpedanceHz) {
+    iDielectricConst = _.toString(iDielectricConst);
+    if (iDielectricConst == '') {
+        return 0;
+    }
+    if (!/=/.test(iDielectricConst)) {
+        return _.toNumber(iDielectricConst);
+    }
+    var _hz = function(v) {
+        if (/g/i.test(v)) {
+            return  _.toNumber(v.replace(/g/i, '')) * 1000 * 1000;
+        } else if (/m/i.test(v)) {v
+            return _.toNumber(v.replace(/m/i, '')) * 1000;
+        } else {
+            return _.toNumber(v);
+        }
+    };
+    var options = iDielectricConst.split(';');
+    return _.chain(options)
+        .filter(function(item){ return item.split('=').length == 2; })
+        .reduce(function(prev, curr) {
+            var temp = curr.replace(/^\s+|\s+$/g, '').split('=');
+            var diff = Math.abs(_hz(iImpedanceHz) - _hz(temp[0]));
+            if (prev.diff == -1 || diff < prev.diff) {
+                prev.diff = diff;
+                prev.value = _.toNumber(temp[1]);
+            }
+            return prev;
+        }, { diff: -1 })
+        .value().value;
+}
+
+var r = getEr("1G=4.15;2G=4.5", "1.49G");
+print("r = ", r);
+r = getEr("4.3", "2G");
+print("r = ", r);
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