Now that you have learned how to use negations, we can describe a new logic of the program that will work without errors.
We need to combine two separate checks into one single check. The project can be started if:
- there are enough developers
-
and they have the knowledge of the technologies
-
and no developers are on vacation
-
and no developers are out sick.
Implementing this logic in the code is quite easy, because negations can be combined with other logical operators. Example:
var conditionOne = true;
var conditionTwo = true;
var conditionThree = false;
if (conditionOne && conditionTwo && !conditionThree) {
// code will be executed
}
It’s time to complete the third program of this work day!
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Simple fork</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/if-else">2. Let’s use an alternative</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/simple-compare">3. Simple comparisons</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/or-equal">4. Comparisons permitting equality</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/equality">5. Equality, inequality</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/string-compare">6. Strict string comparison</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/numeric-compare">7. Strict number comparison</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/then-action">8. Condition-based actions</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/else-action">9. If the condition is not fulfilled</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/value-condition">10. Values as a condition</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/nested-if">11. Nested conditions</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/and-or">12. Logical operators: &&, ||</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/negation">13. Logic traps</a></li><li class="main-nav__course-contents-item"><a href="/courses/javascript-programming/conditions/nesting-deeper">14. 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3.896.106.328.5.46.78.26.273.192.653.06.745-.26.735-2.66-1.6-5.728-3.766-7.16z" fill="#F1662A"/></svg></span><p class="course-loading-overlay__message"><b class="course-loading-overlay__message-title">Loading…</b><br><span class="course-loading-overlay__message-text">Everything will be ready in few seconds</span></p></div></div><div class="course-layout__sidebar course-theory"><div class="course-theory__inner course-theory__inner--left-stub"><button class="course-theory__close icon-close icon-close--light" type="button">Close</button><ul class="course-tabs course-tabs--non-interactive course-layout__theory-heading js--theory-tabs"><li class="course-tabs__item course-tabs__item--external course-tab course-tab--centered"><span class="course-tab__icon"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-theory"></use></svg></span><span class="course-tab__title">Theory</span></li><li class="course-tabs__item course-tabs__item--internal course-tab course-tab--centered course-tab--active js--theory-tab__theory"><span class="course-tab__icon"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-theory"></use></svg></span><span class="course-tab__title">Theory</span></li><li class="course-tabs__item course-tabs__item--internal course-tab course-tab--centered js--theory-tab__comments"><span class="course-tab__icon"><svg aria-hidden="true" style="width: 16px; height: 16px; fill: #2e2c9c;"><use xlink:href="/img/sprites/up.svg#comment"></use></svg></span><span class="course-tab__title">Comments</span></li></ul><section class="course-theory__content"><div class="js--theory-pane__theory course-theory__content-inner"><h1 class="course-theory__content-heading">Let’s combine logical operators</h1><div class="course-theory__content-text"><p>Now that you have learned how to use negations, we can describe a new logic of the program that will work without errors.</p><p>We need to combine two separate checks into one single check. The project can be started if:</p><ul><li>there are enough developers</li><li><em>and</em> they have the knowledge of the technologies</li><li><em>and</em> no developers are on vacation</li><li><em>and</em> no developers are out sick.</li></ul><p>Implementing this logic in the code is quite easy, because negations can be combined with other logical operators. Example:</p><pre><code>var conditionOne = true;
var conditionTwo = true;
var conditionThree = false;
if (conditionOne && conditionTwo && !conditionThree) {
// code will be executed
}</code></pre><p>It’s time to complete the third program of this work day!</p></div></div><div class="js--theory-pane__comments hidden course-theory__content-inner"><div class="course-theory__content-text"><h2 class="course-theory__content-heading">Comments</h2><div id="disqus_thread"></div><script>
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</script><noscript>Please enable JavaScript to view the <a href="https://disqus.com/?ref_noscript">comments powered by Disqus.</a></noscript></div></div></section><div class="course-theory__controls"><button class="button button--close" type="button">To the task</button></div></div></div><div class="course-layout__column course-layout__column--left"><ul class="js--course-tabs course-tabs course-layout__course-tabs"><li class="course-tabs__item course-tab js--editor-tab course-tabs__item--limited course-tabs__item--limited-large course-tab--active" data-editor="js"><span class="course-tab__title course-tab__title--indent"><span class="course-tab__title-part course-tab__title-part--active">script.js</span></span></li></ul><div class="course-layout__editors"><div class="js--editor course-editor course-layout__editor" id="" data-tab="js" data-split=""><span class="course-editor__label"><span class="course-editor__label-item">JavaScript</span></span><div class="course-editor__item" id="js-editor">var enoughDevelopers = false;
var techAvailable = false;
var onVacation = false;
var onSickLeave = false;
if (enoughDevelopers && techAvailable) {
console.log('You can start the project');
}
</div></div></div><div class="course-editor-controls"><button class="course-editor-controls__item course-editor-controls__item--answer" type="button">Show the answer</button></div><div class="js--feedback course-unhappy"><button class="js--feedback-btn course-unhappy__button" type="button"><span class="sr-only">Complain</span><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#unhappy"></use></svg></button><div class="js--feedback-modal course-unhappy__modal course-unhappy__modal--step-one"><form method="POST" action="/courses/javascript-programming/conditions/logic-operators/signal" class="course-unhappy__form form"><input type="hidden" name="csrf_name" value="csrf69aea7e3c61ad"><input type="hidden" name="csrf_value" value="82585f0e50daa5afe07cc447fa58c521"><p class="course-unhappy__text">What didn’t you like in this task?</p><div class="course-unhappy__slide"><div class="course-unhappy__wrap"><div class="course-unhappy__list"><label class="checkbox checkbox--small"><input class="checkbox__input" name="problems" value="1" type="checkbox"><span class="checkbox__text">The code check doesn’t work</span></label><label class="checkbox checkbox--small"><input class="checkbox__input" name="problems" value="2" type="checkbox"><span class="checkbox__text">The task is too difficult</span></label><label class="checkbox checkbox--small"><input class="checkbox__input" name="problems" value="3" type="checkbox"><span class="checkbox__text">The theory is hard to understand</span></label><label class="checkbox checkbox--small"><input class="js--feedback-other-checkbox checkbox__input" name="problems" value="0" type="checkbox"><span class="checkbox__text">Other (will write below)</span></label></div><div class="course-unhappy__message"><label class="sr-only" for="id-message">Другое (сейчас напишу)</label><textarea class="field field--area" id="id-message" name="message" placeholder="For example, a typo in the word «heading»"></textarea></div></div></div><button class="course-unhappy__control course-unhappy__control--prev" type="button"><span class="sr-only">Prev</span><svg aria-hidden="true"><use xlink:href="/img/sprites/landings.svg#arrow"></use></svg></button><button class="course-unhappy__control course-unhappy__control--next" type="button" disabled><span class="sr-only">Next</span><svg aria-hidden="true"><use xlink:href="/img/sprites/landings.svg#arrow"></use></svg></button><button class="js--submit-btn button" disabled>Submit</button></form><p class="course-unhappy__result hidden">Thanks! We’ll fix everything at once!</p></div></div></div><div class="course-layout__column course-layout__column--right"><span class="course-separator-control"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-arrows-separator"></use></svg></span><div class="course-browser"><div class="course-browser__menu"><span class="course-browser__menu-item course-browser__address"><span class="course-browser__menu-item-inner">Console</span></span><button class="js--autorun course-browser__menu-item course-browser__menu-button course-browser__menu-button--text-with-icon course-browser__menu-button--autorun course-browser__menu-button--autorun-on" title="Autorun" type="button"><span class="course-browser__menu-item-inner"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-autorun"></use></svg>
Autorun
</span></button><button class="course-browser__menu-item course-browser__menu-button course-browser__menu-button--expand" type="button"><svg xmlns="http://www.w3.org/2000/svg" width="11" height="11" viewBox="0 0 11 11"><path d="M1.375 5.125v4.5h4.5m3.75-3.75v-4.5h-4.5" fill="none" fill-rule="evenodd" stroke="currentColor"></path></svg></button></div><div class="course-browser__notification js--browser-change-heading hidden"><p class="course-browser__notification-text">The code has changed, click “Run” or turn autorun on.</p><button class="course-browser__notification-button course-browser__notification-button--play js--close" type="button"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-play"></use></svg>
Run</button></div><div class="course-browser__content"><div class="console js--console"><h2 class="sr-only">Result</h2><div class="console__content js--console__content"></div></div></div><div class="course-goals js--goals"><div class="course-goals__heading"><span class="course-goals__heading-title"><span class="course-goals__count-label">Goals</span><span class="course-goals__count">completed</span></span><button class="course-goals__button course-goals__button--expand js--goals__expand" type="button"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#icon-collapse"></use></svg></button><a class="course-goals__button course-goals__button--next button button--green button--without-border hidden" href="/courses/javascript-programming/conditions/summary" title="Summary of “Conditions”"><svg aria-hidden="true"><use xlink:href="/img/sprites/courses.svg#arrow-white--mini"></use></svg></a></div><div class="course-goals__content"><p>Let’s complete the program and check its behavior.</p><ol class="course-goals__list"><li class="course-goals__list-item">Add <code>!onVacation</code> condition at the end of the check using “logical AND”<span class="mark">.</span></li><li class="course-goals__list-item">And after it, also using “logical AND” <code>!onSickLeave</code> condition<span class="mark">.</span></li><li class="course-goals__list-item">Now add the <code>else</code> fork and log the <code>'You cannot start the project'</code> message in it.</li><li class="course-goals__list-item">Correct the values of the variables so that the condition is fulfilled.</li><li class="course-goals__list-item">Then indicate that someone from the developers is on vacation and make sure that the project cannot be started.</li></ol></div></div></div></div></article></div><div class="course-interface__overlay course-interface__overlay--active"></div></main><script
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