June 2018 Update

Task/Number-names/JavaScript/number-names.js

@@ -0,0 +1,44 @@
+const divMod = y => x => [Math.floor(y/x), y % x];
+
+const sayNumber = value => {
+  let name = '';
+  let quotient, remainder;
+  const dm = divMod(value);
+  const units = ['zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven',
+    'eight', 'nine', 'ten', 'eleven', 'twelve', 'thirteen', 'fourteen',
+    'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen'];
+  const tens = ['', '', 'twenty', 'thirty', 'forty', 'fifty', 'sixty',
+    'seventy', 'eighty', 'ninety'];
+  const big = [...['', 'thousand'], ...['m', 'b', 'tr', 'quadr', 'quint',
+    'sext', 'sept', 'oct', 'non', 'dec'].map(e => `${e}illion`)];
+
+  if (value < 0) {
+    name = `negative ${sayNumber(-value)}`
+  } else if (value < 20) {
+    name = units[value]
+  } else if (value < 100) {
+    [quotient, remainder] = dm(10);
+    name = `${tens[quotient]} ${units[remainder]}`.replace(' zero', '');
+  } else if (value < 1000) {
+    [quotient, remainder] = dm(100);
+    name = `${sayNumber(quotient)} hundred and ${sayNumber(remainder)}`
+      .replace(' and zero', '')
+  } else {
+    const chunks = [];
+    const text = [];
+    while (value !== 0) {
+      [value, remainder] = divMod(value)(1000);
+      chunks.push(remainder);
+    }
+    chunks.forEach((e,i) => {
+      if (e > 0) {
+        text.push(`${sayNumber(e)}${i === 0 ? '' : ' ' + big[i]}`);
+        if (i === 0 && e < 100) {
+          text.push('and');
+        }
+      }
+    });
+    name = text.reverse().join(', ').replace(', and,', ' and');
+  }
+  return name;
+};