Common methods of JS digital thousand bit segmentation

It is a very common problem to convert ordinary numbers into numeric strings with thousand separator format ,
The rule of thousands separator format is that the integer part of a number is set every three digits , With “,” Section by section . Fractional parts are not segmented .
Example ：12,345,678.23456
notes ： Only aim at number So do not do other types of verification

Method 1 ： Traverse every 3 Bit add " , "

	const numFormat1 = param => {
    
		const num = param + '';
		const numGroup = num.includes('.') ? num.split('.') : [num];
		const intFn = numStr =>
			numStr
				.split('')
				.reverse()
				.reduce((prev, next, index) => {
    
					return (index % 3 ? next : next + ',') + prev;
				});
		const intNum = intFn(numGroup[0]);
		const floatNum = numGroup[1] ? '.' + numGroup[1] : '';
		return intNum + floatNum;
	};

Method 2 ：toLocaleString

Use JS Self contained function toLocaleString

numObj.toLocaleString([locales [, options]]) notes : The decimal part is automatically rounded

toLocaleString() Method returns the representation string of this number in a specific language environment .

	let num1 = 12345678912345;
	let num2 = 987654.321056;
	
	console.log(num1.toLocaleString());  // "12,345,678,912,345"
	console.log(num2.toLocaleString());  // "987,654.321" （ The decimal part is rounded off ）

Method 3 ： Regular matching and replace

str.replace(regexp|substr, newSubStr|function)

	const numFormat = num => {
    
	  return num.toString().replace(/\d+/, function(n){
     //  First extract the integer part 
	       return n.replace(/(\d)(?=(\d{3})+$)/g, function($1){
    
	          return $1 + ",";
	       });
	  })
	}