replace all special characters expect first occurrence of-CodePudding

I want to replace everything other than numeric char from a string, but if appears at the starting of the string it should be ignored. for example

1234  !@#$%^&*()_ =-;',.><:" becomes 1234
 1234 becomes  1234
    1234 becomes  1234
 1234  !@#$%^&*()_ =-;',.><:" becomes  1234
 1234  !@#$%^&*()_ =-;',.><:" becomes  1234
 1234ABCabc  !@#$%^&*()_ =-;',.><:" becomes  1234
1234ABCabc  !@#$%^&*()_ =-;',.><:" becomes 1234
Aa1234ABCabc  !@#$%^&*()_ =-;',.><:" becomes 1234
a 1234ABCabc  !@#$%^&*()_ =-;',.><:" becomes 1234
1 1234ABCabc  !@#$%^&*()_ =-;',.><:" becomes 11234

can you please suggest?

CodePudding user response：

You can try:

str.replace(/((?<!^)\D)|(^[^ 0-9])/g, '');

This replaces (with nothing):

any non-digit that is not at the start of the string.
any non-digit except that is at the start of the string.

CodePudding user response：

This extracts numbers from a string, including an optional leading :

var tests = [
  '1234  !@#$%^&*()_ =-;\',.><:"', // becomes 1234
  ' 1234', // becomes  1234
  '    1234', // becomes  1234
  ' 1234  !@#$%^&*()_ =-;\',.><:"', // becomes  1234
  ' 1234  !@#$%^&*()_ =-;\',.><:"', // becomes  1234
  ' 1234ABCabc  !@#$%^&*()_ =-;\',.><:"', // becomes  1234
  '1234ABCabc  !@#$%^&*()_ =-;\',.><:"', // becomes 1234
  'Aa1234ABCabc  !@#$%^&*()_ =-;\',.><:"', // becomes 1234
  'a 1234ABCabc  !@#$%^&*()_ =-;\',.><:"', // becomes 1234
  '1 1234ABCabc  !@#$%^&*()_ =-;\',.><:"' // becomes 11234
];

tests.forEach(str => {
  console.log(str   ' => '   str.replace(/^.*?(\ ?[0-9] ).*$/, '$1'));
});

Output:

1234  !@#$%^&*()_ =-;',.><:" => 1234
VM1036:2  1234 =>  1234
VM1036:2     1234 =>  1234
2VM1036:2  1234  !@#$%^&*()_ =-;',.><:" =>  1234
VM1036:2  1234ABCabc  !@#$%^&*()_ =-;',.><:" =>  1234
VM1036:2 1234ABCabc  !@#$%^&*()_ =-;',.><:" => 1234
VM1036:2 Aa1234ABCabc  !@#$%^&*()_ =-;',.><:" => 1234
VM1036:2 a 1234ABCabc  !@#$%^&*()_ =-;',.><:" =>  1234
VM1036:2 1 1234ABCabc  !@#$%^&*()_ =-;',.><:" => 1

Your described objective and last example contradict each other. Please be more specific what you need.