Color string conversion

Color string conversion

subject ：
take rgb The color string is converted to hexadecimal form , Such as rgb(255, 255, 255) To #ffffff

1. rgb Each of them , The number of spaces after is not fixed
2. Hexadecimal expressions use six lowercase letters
3. If the input does not match rgb Format , Return to original input

answer ：

function rgb2hex(sRGB) {
    
    var reg = /rgb\((\d+),\s*(\d+),\s*(\d+)\)/;
	var arr = sRGB.match((reg));
    if(!arr){
    
        return sRGB;
    }else{
    
        var num1 = Number(arr[1])<16?'0'+Number(arr[1]):Number(arr[1]);
	    var num2 = Number(arr[2])<16?'0'+Number(arr[2]):Number(arr[2]);
	    var num3 = Number(arr[3])<16?'0'+Number(arr[3]):Number(arr[3]);
	    var num = "#" + num1.toString(16)+ num2.toString(16)+ num3.toString(16);
	    return num;
    }
}

match() Method

Match the lookup string , Returns the part that matches the content of the regular expression , The return value is an array type , If not found, return null.

// If the regular expression is not used g
console.log('123ssss 123 sss f123fff'.match(/fff/)); //['fff', index: 20, input: '123ssss 123 sss f123fff', groups: undefined]
// If regular expressions use g, There is no following content 
console.log('xxxssss sss ffff'.match(/xxx/g)); //['xxx']

toString() Method

Convert to string type , The parameter is hexadecimal , If every write parameter defaults to 10. for example ：2,8,16,…

Knowledge point ： Regular expressions 、toString(16) Convert base