Introduction to 3 AngularJS directives that can improve user experience_AngularJS

1. Avatar picture

In order to display an avatar image in your app, you need to take the user's email address, convert the address to lowercase and encrypt the string using md5. So the smart thing to do is to use instructions to do this and reuse them.

 
/*
 * A simple Gravatar Directive
 * @example
 *  <gravatar-image email="test@email.com" size="50"></gravatar-image>
 */
app.directive('gravatarImage', function () {
 return {
  restrict: 'AE',
  replace: true,
  required: 'email',
  template: '<img ng-src="https://www.gravatar.com/avatar/{{hash}}&#63;s={{size}}&d=identicon" />',
  link: function (scope, element, attrs) {
   attrs.$observe('email', function (value) {
    if(!value) { return; }
 
    // MD5 (Message-Digest Algorithm) by WebToolkit
    var md5=function(s){function L(k,d){return(k<<d)|(k>>>(32-d));}function K(G,k){var I,d,F,H,x;F=(G&2147483648);H=(k&2147483648);I=(G&1073741824);d=(k&1073741824);x=(G&1073741823)+(k&1073741823);if(I&d){return(x^2147483648^F^H);}if(I|d){if(x&1073741824){return(x^3221225472^F^H);}else{return(x^1073741824^F^H);}}else{return(x^F^H);}}function r(d,F,k){return(d&F)|((~d)&k);}function q(d,F,k){return(d&k)|(F&(~k));}function p(d,F,k){return(d^F^k);}function n(d,F,k){return(F^(d|(~k)));}function u(G,F,aa,Z,k,H,I){G=K(G,K(K(r(F,aa,Z),k),I));return K(L(G,H),F);}function f(G,F,aa,Z,k,H,I){G=K(G,K(K(q(F,aa,Z),k),I));return K(L(G,H),F);}function D(G,F,aa,Z,k,H,I){G=K(G,K(K(p(F,aa,Z),k),I));return K(L(G,H),F);}function t(G,F,aa,Z,k,H,I){G=K(G,K(K(n(F,aa,Z),k),I));return K(L(G,H),F);}function e(G){var Z;var F=G.length;var x=F+8;var k=(x-(x%64))/64;var I=(k+1)*16;var aa=Array(I-1);var d=0;var H=0;while(H<F){Z=(H-(H%4))/4;d=(H%4)*8;aa[Z]=(aa[Z]|(G.charCodeAt(H)<<d));H++;}Z=(H-(H%4))/4;d=(H%4)*8;aa[Z]=aa[Z]|(128<<d);aa[I-2]=F<<3;aa[I-1]=F>>>29;return aa;}function B(x){var k="",F="",G,d;for(d=0;d<=3;d++){G=(x>>>(d*8))&255;F="0"+G.toString(16);k=k+F.substr(F.length-2,2);}return k;}function J(k){k=k.replace(/rn/g,"n");var d="";for(var F=0;F<k.length;F++){var x=k.charCodeAt(F);if(x<128){d+=String.fromCharCode(x);}else{if((x>127)&&(x<2048)){d+=String.fromCharCode((x>>6)|192);d+=String.fromCharCode((x&63)|128);}else{d+=String.fromCharCode((x>>12)|224);d+=String.fromCharCode(((x>>6)&63)|128);d+=String.fromCharCode((x&63)|128);}}}return d;}var C=Array();var P,h,E,v,g,Y,X,W,V;var S=7,Q=12,N=17,M=22;var A=5,z=9,y=14,w=20;var o=4,m=11,l=16,j=23;var U=6,T=10,R=15,O=21;s=J(s);C=e(s);Y=1732584193;X=4023233417;W=2562383102;V=271733878;for(P=0;P<C.length;P+=16){h=Y;E=X;v=W;g=V;Y=u(Y,X,W,V,C[P+0],S,3614090360);V=u(V,Y,X,W,C[P+1],Q,3905402710);W=u(W,V,Y,X,C[P+2],N,606105819);X=u(X,W,V,Y,C[P+3],M,3250441966);Y=u(Y,X,W,V,C[P+4],S,4118548399);V=u(V,Y,X,W,C[P+5],Q,1200080426);W=u(W,V,Y,X,C[P+6],N,2821735955);X=u(X,W,V,Y,C[P+7],M,4249261313);Y=u(Y,X,W,V,C[P+8],S,1770035416);V=u(V,Y,X,W,C[P+9],Q,2336552879);W=u(W,V,Y,X,C[P+10],N,4294925233);X=u(X,W,V,Y,C[P+11],M,2304563134);Y=u(Y,X,W,V,C[P+12],S,1804603682);V=u(V,Y,X,W,C[P+13],Q,4254626195);W=u(W,V,Y,X,C[P+14],N,2792965006);X=u(X,W,V,Y,C[P+15],M,1236535329);Y=f(Y,X,W,V,C[P+1],A,4129170786);V=f(V,Y,X,W,C[P+6],z,3225465664);W=f(W,V,Y,X,C[P+11],y,643717713);X=f(X,W,V,Y,C[P+0],w,3921069994);Y=f(Y,X,W,V,C[P+5],A,3593408605);V=f(V,Y,X,W,C[P+10],z,38016083);W=f(W,V,Y,X,C[P+15],y,3634488961);X=f(X,W,V,Y,C[P+4],w,3889429448);Y=f(Y,X,W,V,C[P+9],A,568446438);V=f(V,Y,X,W,C[P+14],z,3275163606);W=f(W,V,Y,X,C[P+3],y,4107603335);X=f(X,W,V,Y,C[P+8],w,1163531501);Y=f(Y,X,W,V,C[P+13],A,2850285829);V=f(V,Y,X,W,C[P+2],z,4243563512);W=f(W,V,Y,X,C[P+7],y,1735328473);X=f(X,W,V,Y,C[P+12],w,2368359562);Y=D(Y,X,W,V,C[P+5],o,4294588738);V=D(V,Y,X,W,C[P+8],m,2272392833);W=D(W,V,Y,X,C[P+11],l,1839030562);X=D(X,W,V,Y,C[P+14],j,4259657740);Y=D(Y,X,W,V,C[P+1],o,2763975236);V=D(V,Y,X,W,C[P+4],m,1272893353);W=D(W,V,Y,X,C[P+7],l,4139469664);X=D(X,W,V,Y,C[P+10],j,3200236656);Y=D(Y,X,W,V,C[P+13],o,681279174);V=D(V,Y,X,W,C[P+0],m,3936430074);W=D(W,V,Y,X,C[P+3],l,3572445317);X=D(X,W,V,Y,C[P+6],j,76029189);Y=D(Y,X,W,V,C[P+9],o,3654602809);V=D(V,Y,X,W,C[P+12],m,3873151461);W=D(W,V,Y,X,C[P+15],l,530742520);X=D(X,W,V,Y,C[P+2],j,3299628645);Y=t(Y,X,W,V,C[P+0],U,4096336452);V=t(V,Y,X,W,C[P+7],T,1126891415);W=t(W,V,Y,X,C[P+14],R,2878612391);X=t(X,W,V,Y,C[P+5],O,4237533241);Y=t(Y,X,W,V,C[P+12],U,1700485571);V=t(V,Y,X,W,C[P+3],T,2399980690);W=t(W,V,Y,X,C[P+10],R,4293915773);X=t(X,W,V,Y,C[P+1],O,2240044497);Y=t(Y,X,W,V,C[P+8],U,1873313359);V=t(V,Y,X,W,C[P+15],T,4264355552);W=t(W,V,Y,X,C[P+6],R,2734768916);X=t(X,W,V,Y,C[P+13],O,1309151649);Y=t(Y,X,W,V,C[P+4],U,4149444226);V=t(V,Y,X,W,C[P+11],T,3174756917);W=t(W,V,Y,X,C[P+2],R,718787259);X=t(X,W,V,Y,C[P+9],O,3951481745);Y=K(Y,h);X=K(X,E);W=K(W,v);V=K(V,g);}var i=B(Y)+B(X)+B(W)+B(V);return i.toLowerCase();};
 
    scope.hash = md5(value.toLowerCase());
    scope.size = attrs.size;
 
    if(angular.isUndefined(scope.size)) {
     scope.size = 60; // default to 60 pixels
    }
   });
  }
 };
});

2. Follow me

This is actually a very short command, but a great one. In the example below, the user clicks on a link, and the displayed input box needs to automatically gain focus. This way, the user no longer has to manually click on the text field when the page is displayed.

/**
 * Sets focus to this element if the value of focus-me is true.
 * @example
 * <a ng-click="addName=true">add name</a>
 * <input ng-show="addName" type="text" ng-model="name" focus-me="{{addName}}" />
 */
app.directive('focusMe', ['$timeout', function($timeout) {
 return {
  scope: { trigger: '@focusMe' },
  link: function(scope, element) {
   scope.$watch('trigger', function(value) {
    if(value === "true") {
     $timeout(function() {
      element[0].focus();
     });
    }
   });
  }
 };
}]);

3.Contenteditable element model binding

The main reason why we use contenteditable instead of textarea elements is that there are no restrictions in layout and UI using the former. We can use this instruction in the editor to achieve a two-way binding between the html and ng-model of the contenteditable element. Currently, ng-model is not supported in contenteditable elements.

/**
 * Two-way data binding for contenteditable elements with ng-model.
 * @example
 *  <p contenteditable="true" ng-model="text"></p>
 */
app.directive('contenteditable', function() {
 return {
  require: '&#63;ngModel',
  link: function(scope, element, attrs, ctrl) {
 
   // Do nothing if this is not bound to a model
   if (!ctrl) { return; }
 
   // Checks for updates (input or pressing ENTER)
   // view -> model
   element.bind('input enterKey', function() {
    var rerender = false;
    var html = element.html();
 
    if (attrs.noLineBreaks) {
     html = html.replace(/<div>/g, '').replace(/<br>/g, '').replace(/<\/div>/g, '');
     rerender = true;
    }
 
    scope.$apply(function() {
     ctrl.$setViewValue(html);
     if(rerender) {
      ctrl.$render();
     }
    });
   });
 
   element.keyup(function(e){
    if(e.keyCode === 13){
     element.trigger('enterKey');
    }
   });
 
   // model -> view
   ctrl.$render = function() {
    element.html(ctrl.$viewValue);
   };
 
   // load init value from DOM
   ctrl.$render();
  }
 };
});

Conclusion: AngularJS directives can be used to improve user experience

I hope that after the introduction in this article, you will realize the usefulness of AngularJS instructions.

For me, directives are the most exciting feature in AngularJS. How incredibly powerful it is to create reusable components that can be added to a library of pure HTML applications. Because the instructions are practical and most instructions are not difficult to write, many developers have already developed many instructions for currently popular libraries. For example, the AngularJS team has created a series of directives for Bootstrap (does anyone still use it?), called UI Bootstrap.