freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/basic-javascript/use-conditional-logic-with-if-statements.md

id, challengeType, videoUrl, forumTopicId, title

id	challengeType	videoUrl	forumTopicId	title
cf1111c1c12feddfaeb3bdef	1	https://scrimba.com/c/cy87mf3	18348	用 if 语句来表达条件逻辑

Description

If语句用于在代码中做条件判断。关键字if告诉 JavaScript 在小括号中的条件为真的情况下去执行定义在大括号里面的代码。这种条件被称为Boolean条件，因为他们只可能是true（真）或false（假）。 当条件的计算结果为true，程序执行大括号内的语句。当布尔条件的计算结果为false，大括号内的代码将不会执行。 伪代码

if(条件为真){
语句被执行
}

示例

function test (myCondition) {
  if (myCondition) {
     return "It was true";
  }
  return "It was false";
}
test(true);  // returns "It was true"
test(false); // returns "It was false"

当test被调用，并且传递进来的参数值为true，if语句会计算myCondition的结果，看它是真还是假。如果条件为true，函数会返回"It was true"。当test被调用，并且传递进来的参数值为false，myCondition不 为true，并且不执行大括号后面的语句，函数返回"It was false"。

Instructions

在函数内部创建一个if语句，如果该参数wasThatTrue值为true，返回"Yes, that was true"，否则，并返回"No, that was false"。

Tests

tests:
  - text: <code>trueOrFalse</code>应该是一个函数。
    testString: assert(typeof trueOrFalse === "function");
  - text: <code>trueOrFalse(true)</code>应该返回一个字符串。
    testString: assert(typeof trueOrFalse(true) === "string");
  - text: <code>trueOrFalse(false)</code>应该返回一个字符串。
    testString: assert(typeof trueOrFalse(false) === "string");
  - text: <code>trueOrFalse(true)</code>应该返回 "Yes, that was true"。
    testString: assert(trueOrFalse(true) === "Yes, that was true");
  - text: <code>trueOrFalse(false)</code>应该返回 "No, that was false"。
    testString: assert(trueOrFalse(false) === "No, that was false");

Challenge Seed

// Example
function ourTrueOrFalse(isItTrue) {
  if (isItTrue) {
    return "Yes, it's true";
  }
  return "No, it's false";
}

// Setup
function trueOrFalse(wasThatTrue) {

  // Only change code below this line.



  // Only change code above this line.

}

// Change this value to test
trueOrFalse(true);

Solution

function trueOrFalse(wasThatTrue) {
  if (wasThatTrue) {
    return "Yes, that was true";
  }
  return "No, that was false";
}