{"id":23170,"date":"2022-11-24T09:09:43","date_gmt":"2022-11-24T03:39:43","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-alert-not-working-in-jsp\/"},"modified":"2022-11-24T09:09:43","modified_gmt":"2022-11-24T03:39:43","slug":"solved-alert-not-working-in-jsp","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-alert-not-working-in-jsp\/","title":{"rendered":"[Solved] alert() not working in JSP"},"content":{"rendered":"

[ad_1]
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You’re very much confusing the difference between server-side code and client-side code. Conceptually think of them as entirely separate. Your server-side code is this:<\/p>\n

boolean check = false;\nSystem.out.println(\"this runs ! \");\n<\/code><\/pre>\n
Two things to notice:<\/p>\n
    \n
  1. You define a variable that you never use.<\/li>\n
  2. The message will always print to the output because there’s no reason why it shouldn’t.<\/li>\n<\/ol>\n
    Your client-side code is this:<\/p>\n
    function test(){\n\n    if(!check) {\n        alert(\"validation fails\");\n        return false;\n    }\n    else return true;\n\n}\n<\/code><\/pre>\n
    If you’re successfully invoking test()<\/code> you’ll find that this will produce an error on the browser’s console because check<\/code> is undefined.<\/p>\n
    \n
    As for how to correct this<\/em><\/strong>, that really depends on what you’re actually trying to do here.  “I want to use a Java variable in JavaScript” is not the problem you’re trying to solve.  Stepping back from that, there must be a reason<\/em> behind writing this code.  Whatever that reason is, it’s very likely<\/em> that there’s a better way to do this than to continue down this path, given that you took a wrong turn on the path a while<\/em> ago.<\/p>\n
    However, if all you want is to output that variable to JavaScript, you may be able to do something like this:<\/p>\n
    if(<%=!check%>) {\n    alert(\"validation fails\");\n    return false;\n}\n<\/code><\/pre>\n
    This would output the result of evaluating !check<\/code> on the server<\/em>, and that result would be a raw string embedded in the JavaScript code.  I’m not 100%<\/em> sure if Java\/JSP\/etc. evaluates that way, but hopefully you get the idea.  Examine the resulting client-side code to see what it actually outputs of course.  Ideally<\/em> it would end up something like this:<\/p>\n
    if(true) {\n    alert(\"validation fails\");\n    return false;\n}\n<\/code><\/pre>\n
    Granted, if this bit of hand-waving is covering up more problems:<\/p>\n
    \/*\n* java code for updating test variable for validating values on the jsp page\n*\/\n<\/code><\/pre>\n
    Then we won’t be able to determine that within the scope of this question.<\/p>\n<\/p><\/div>\n
    <\/div>\n<\/div>\n
                <\/span> <\/p><\/div>\n<\/div>\n
    [ad_2]<\/p>\n
    solved alert() not working in JSP <\/p>\n","protected":false},"excerpt":{"rendered":"
    [ad_1] You’re very much confusing the difference between server-side code and client-side code. Conceptually think of them as entirely separate. Your server-side code is this: boolean check = false; System.out.println(“this runs ! “); Two things to notice: You define a variable that you never use. The message will always print to the output because there’s … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[323,333,1266],"class_list":["post-23170","post","type-post","status-publish","format-standard","hentry","category-solved","tag-java","tag-javascript","tag-jsp"],"yoast_head":"\n[Solved] alert() not working in JSP - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-alert-not-working-in-jsp\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] alert() not working in JSP - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] You’re very much confusing the difference between server-side code and client-side code. 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