var re = /^(\d{1,7}|\d{1,6}\.\d|\d{1,5}\.\d{1,2})$/;

​

function validate(str) {

  return (str).match(re) !== null;

}

​

function assert(value, expected) {

  return value === expected;

}

​

console.log(

  assert(validate("1234567"), true)

);

​

console.log(

  assert(validate("123456.7"), true)

);

​

console.log(

  assert(validate("12345.67"), true)

);

​

console.log(

  assert(validate("1234.567"), false)

);

​

console.log(

  assert(validate("12345.678"), false)

);

​

console.log(

  assert(validate("123456.78"), false)

);

​

console.log(

  assert(validate("1234567.8"), false)

);

​

console.log(

  assert(validate("12345678"), false)

);