{"id":630,"date":"2024-07-30T19:36:04","date_gmt":"2024-07-30T17:36:04","guid":{"rendered":"https:\/\/blog.sutilweb.eu\/?page_id=630"},"modified":"2024-07-30T19:36:04","modified_gmt":"2024-07-30T17:36:04","slug":"001-variables-var-vs-let","status":"publish","type":"page","link":"https:\/\/sutilweb.eu\/index.php\/lenguajes\/javascript\/javascript-practico\/03-tipos-de-datos-en-javascript\/001-variables-var-vs-let\/","title":{"rendered":"001. Variables: var VS let"},"content":{"rendered":"\n<p>En este cap\u00edtulo veremos lo que es una <strong>variable<\/strong> y como declararla de la forma correcta.<\/p>\n\n\n\n<!--more-->\n\n\n\n<h2 class=\"wp-block-heading\">Qu\u00e9 es una variable<\/h2>\n\n\n\n<p>Una variable en <strong>Javascript<\/strong> es un lugar en la memoria de nuestra computadora para almacenar <strong>datos<\/strong>. Una <strong>variable<\/strong> en <strong>Javascript<\/strong> se declara de la siguiente manera.<\/p>\n\n\n\n<p><strong>Ejm<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">var hola = 'Hola Mundo';\nconsole.log(hola);<\/pre>\n\n\n\n<p>Las <strong>variables<\/strong> en los <strong>lenguajes de programaci\u00f3n<\/strong> tienen un <strong>\u00e1mbito de existencia<\/strong>, lo que se conoce como el <strong>scope<\/strong> de las variables. <strong>Javascript<\/strong>, antes del a\u00f1o 2015, es decir, antes del <strong>ES6<\/strong>, ten\u00eda el <strong>scope global<\/strong> (variables que existen dentro de todo el documento) y un <strong>scope funcional<\/strong> (variables que existen dentro de <strong>funciones<\/strong>), pero no exist\u00eda un <strong>\u00e1mbito de bloque<\/strong> como ocurr\u00eda con otros lenguajes de programaci\u00f3n como <strong>Java<\/strong> o <strong>C<\/strong>. A partir de <strong>ES6<\/strong> ya podemos crear <strong>variables de \u00e1mbito de bloque<\/strong>, lo hacemos sustituyendo la palabra reservada <strong><em>var<\/em> <\/strong>por la palabra reservada <strong><em>let<\/em><\/strong>.<\/p>\n\n\n\n<p>Hay que entender que si declaramos una <strong>variable<\/strong> con <strong><em>var<\/em><\/strong>, esa variable va a tener <strong>\u00e1mbito global<\/strong>, mientras que si la declaramos con <strong><em>let<\/em><\/strong>, s\u00f3lo va a tener <strong>\u00e1mbito de bloque<\/strong>. A d\u00eda de hoy se considera mala pr\u00e1ctica utilizar <strong><em>var<\/em><\/strong>, se ha de utilizar <strong><em>let<\/em><\/strong>.<\/p>\n\n\n\n<p>El objeto que almacena las variables en <strong>Javascript<\/strong> declaradas con la palabra reservada <strong><em>var<\/em> <\/strong>es el objeto <strong><em>window<\/em><\/strong>, que es el objeto que mapea toda la ventana del navegador para <strong>Javascript<\/strong>. Con la palabra reservada <strong><em>let<\/em><\/strong>, la variable no se guarda en el objeto <strong><em>window<\/em><\/strong>.<\/p>\n\n\n\n<p>En resumen, <strong><em>var<\/em> <\/strong>genera <strong>variables globales<\/strong>, mientras que <strong><em>let<\/em> <\/strong>genera <strong>variables de bloque<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Comentarios en Javascript<\/h2>\n\n\n\n<p>Para los comentarios existen dos t\u00e9cnicas<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\/\/ Comentarios en una \u00fanica l\u00ednea<\/li>\n\n\n\n<li>\/* Comentarios en varias l\u00edneas *\/<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>En este cap\u00edtulo veremos lo que es una variable y como declararla de la forma correcta.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":628,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center 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