[游戏开发]determine if a string contains all unique characters.

Task
Write a program to determine if a string contains all unique characters.
Return True/true if it does and False/false otherwise.

The string may contain any of the 128 ASCII characters.

Specification
hasUniqueChars(str)
Parameters
str: String - The string that may or may not contain all unique characters

Return Value
Boolean - True if all characters in the string are unique

Examples
str Return Value
“abcdefg” true
“abbcdefg” false

function hasUniqueChars(s) {
    // If at any time we encounter 2
    // same characters, return false
    for(let i = 0; i < s.length; i++)
        for(let j = i + 1; j < s.length; j++)
            if (s[i] == s[j])
                return false;
 
    // If no duplicate characters
    // encountered, return true
    return true;
}

const {assert} = require('chai');

describe('hasUniqueChars()', () => {
  it('Should return false', () => {
    assert.isFalse(hasUniqueChars("  nAa"));
    assert.isFalse(hasUniqueChars("++-"));
  });
   
  it('Should return true', () => { 
    assert.isTrue(hasUniqueChars("abcdef"));
  });
});