[JS IR BE] hashCode, toString, number conversion support

libraries/stdlib/js/irRuntime/numberConversion.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.js
+
+fun asIs(a: dynamic) = a
+
+fun numberToByte(a: dynamic): Byte = toByte(numberToInt(a))
+
+fun numberToDouble(a: dynamic): Double = js("+a").unsafeCast<Double>()
+
+fun numberToInt(a: dynamic): Int = doubleToInt(a)
+
+fun numberToShort(a: dynamic): Short = toShort(numberToInt(a))
+
+// << and >> shifts are used to preserve sign of the number
+fun toByte(a: dynamic): Byte = js("a << 24 >> 24").unsafeCast<Byte>()
+fun toShort(a: dynamic): Short = js("a << 16 >> 16").unsafeCast<Short>()
+
+fun doubleToInt(a: dynamic) = js("""
+    if (a > 2147483647) return 2147483647;
+    if (a < -2147483648) return -2147483648;
+    return a | 0;
+""").unsafeCast<Int>()