Several methods of converting strings to regular objects

1. Use the eval function

2.new Function

3.new RegExp

    let fileIndex = '0-9'
    let reg = '/[a-zA-Z' + fileIndex + '_-]+/'
    var reg1 = eval(reg)
    var reg2 = new Function('return ' + reg)();
    var reg3 = new RegExp(reg)
    console.log(reg1);
    console.log(reg2);
    console.log(reg3);
 
 
    let regCopy = '[a-zA-Z' + fileIndex + '_-]+'
    var reg4 = new RegExp(regCopy)
    console.log(reg4);