regex-替换除单个字母后的空格之外的所有空格

var s = "True that A B C School is great for kids and C D E School is not";
var rx = /\b([a-zA-Z]\s)\b|\s/g;
console.log(
  s.replace(rx, function($0,$1) { return $1 ? $1 : "%"; })
  // ES6+ syntax
  // s.replace(rx, ($0,$1) => $1 ? $1 : "%" )
);
// => True%that%A B C School%is%great%for%kids%and%C D E School%is%not

console.log("[foo bar foobar   barfoo b f f b ]".replace(/([a-z]{2,})(\s+)/gi, "$1#"));

var myString = 'A B C School is great for kids';
    
var result = myString.replace(/\w{2}\s/gi, match => match.replace(' ', '|'))

document.writeln(result)

var regex = /(\B\S|^)\s+/g;

var tests = [
  " ",
  " A B C Test DE",
  "True that A B C School is great for kids and C D E School is not"
];

for ( var i = 0; i < tests.length; i++ )
{
  console.log( `"${tests[i]}" -> "${tests[i].replace( regex, '$1%' )}"` );
}