force decimal notation & cast to string when rounding, fix #2287

exchange/wrappers/binance.js

@@ -186,9 +186,39 @@ Trader.prototype.round = function(amount, tickSize) {
   amount *= precision;
   amount = Math.floor(amount);
   amount /= precision;
+
+  // https://gist.github.com/jiggzson/b5f489af9ad931e3d186
+  amount = this.scientificToDecimal(amount);
+
   return amount;
 };
 
+// https://gist.github.com/jiggzson/b5f489af9ad931e3d186
+Trader.prototype.scientificToDecimal = function(num) {
+  if(/\d+\.?\d*e[\+\-]*\d+/i.test(num)) {
+    const zero = '0';
+    const parts = String(num).toLowerCase().split('e'); // split into coeff and exponent
+    const e = parts.pop(); // store the exponential part
+    const l = Math.abs(e); // get the number of zeros
+    const sign = e/l;
+    const coeff_array = parts[0].split('.');
+    if(sign === -1) {
+      num = zero + '.' + new Array(l).join(zero) + coeff_array.join('');
+    } else {
+      const dec = coeff_array[1];
+      if(dec) {
+        l = l - dec.length;
+      }
+      num = coeff_array.join('') + new Array(l+1).join(zero);
+    }
+  } else {
+    // make sure we always cast to string
+    num = num + '';
+  }
+
+  return num;
+}
+
 Trader.prototype.roundAmount = function(amount) {
   return this.round(amount, this.market.minimalOrder.amount);
 }
@@ -354,8 +384,9 @@ Trader.prototype.cancelOrder = function(order, callback) {
   // callback for cancelOrder should be true if the order was already filled, otherwise false
   const cancel = (err, data) => {
     if (err) {
-      if(data && data.msg === 'UNKNOWN_ORDER') {  // this seems to be the response we get when an order was filled
-        return callback(undefined, true); // tell the thing the order was already filled
+      // when the order was filled
+      if(data && data.msg === 'UNKNOWN_ORDER') {
+        return callback(undefined, true);
       }
       return callback(err);
     }
@@ -371,10 +402,6 @@ Trader.prototype.cancelOrder = function(order, callback) {
   retry(retryForever, fetcher, cancel);
 };
 
-Trader.prototype.initMarkets = function(callback) {
-
-}
-
 Trader.getCapabilities = function() {
   return {
     name: 'Binance',