Add numberWithCommas

Use commas to separate digits。

snippets/numberWithCommas.md

@@ -0,0 +1,19 @@
+### numberWithCommas
+
+Use commas to separate digits。
+
+Use `toString()` to convert the number `num` to a string, then use `/\B(?=(\d{3})+(?!\d))/g` to separate every three characters with a comma,except word boundary。
+
+ ```js
+const toThousands = (num) => {
+  let cleanNum = num.toString().split('').filter(n => '0123456789.'.includes(n)).join('') 
+  let wholeNum = cleanNum.split('.')[0].replace(/\B(?=(\d{3})+(?!\d))/g, ",")
+  let decNum = `.${cleanNum.split('.')[1]}`
+  return wholeNum + decNum;
+}
+
+// toThousands(12305030388.9087) //-> '12,305,030,388.9087'
+// toThousands(123.889087e2) //-> '12,388.9087'
+// toThousands('12305030388.9087') //-> '12,305,030,388.9087'
+// toThousands('12305abc030388.9087') // -> '12,305,030,388.9087'
+```

tag_database

@@ -123,3 +123,4 @@ without:array
 words:string
 zip:array
 zipObject:array
+numberWithCommas:utility