从数组创建JSON对象

Question

I have an input field, #tag_field , where my users enter a tag, which I would then like to check if the specified value exists in the JSON object.

Included below is the code that I'm currently using but am not sure how to pass the user input to the function on the blur() event.

var tags = [
                    {
                        "tag": "php",
                        "id": "x&8j"
                    },
                    {
                        "tag": "ruby",
                        "id": "x&8jX90"
                    }
];

$j('#tag_field').blur(function(){
        var tagMap = {};
        var i = null;
        for (i = 0; tags.length > i; i += 1) {
            tagMap[tags[i].tagName] = tags[i];
        }

        var hasTag = function(tagName) {
            return tagMap[tagName];
        };
    });

Answer 1

Do you mean some like this

Do you just need to take the value of the input and compare it to the names in your tags object?

$('#tag_field').blur(function() {
    var tagMap = {};
    var i = null;
    for (i = 0; tags.length > i; i += 1) {

        if (tags[i].tag == $(this).val()) alert('exist' + tags[i].id)
        //Check
    }

    var hasTag = function(tagName) {
        return tagMap[tagName];
    };
});​

Answer 2

var tags = [
    {
        "tag": "php",
        "id": "x&8j"
    },
    {
       "tag": "ruby",
       "id": "x&8jX90"
    }
]

$(function() { 
    $('#tag_field').on('blur', function(e) {
        var $this = $(this), val = $.trim($this.val());
        if (!val) return false;

        for(var i=0, l=tags.length;i<l;i++) {
            if (tags[i]['tag'] === val) {
                console.log('tag exists')
                return tags[i]['tag'];
            }
        }
        console.log('tag does not exist');
        return false;
    })
})

Simplifying your tag map (if possible) will make it easier still

var tags =  { "php" : "x&8j", "ruby" : "x&8jX90" }

$(function() { 
    $('#tag_field').on('blur', function(e) {
      if(tags[$.trim($(this).val())]) {
          console.log('tag exists')
      } else {
          console.log('tag does not exist')
      }
    })
})
​

Answer 3

You'll be best off using Array.some when available:

function tagExists(needle, haystack) {
  if (Array.prototype.some) {
    return haystack.some(function(element) {
      return element.tag == needle
    });
  } else {
    for(i in haystack) {
      if(typeof(haystack[i]) == 'object' && haystack[i].tag == needle) {
        return true;
      }
    }
    return false;
  }
}

To use it in your specific scenario, something along the lines of:

$('#tag_field').on('blur', function() {
  if(tagExists($(this).val(), tags) {
    // Tag exists. 
  }
});

Note that this is case-sensitive as I defined it but could be tweaked easily by calling String.toLowerCase() on the needle as well as each tag during the comparison.

Finally, perhaps I'm being over picky, but your tag map is not technically a JSON object; it is simply an array of objects.